iOS and Android apps
App development company in London
We design, build, test and launch iOS and Android apps from one codebase, starting with a focused MVP from £9,500 and supporting it long after launch.
- One codebase, both app stores
- Testing built into every sprint
- You own the code
Quick answer
ProntX is a London app development company building iOS and Android apps from one codebase with React Native or Flutter. MVPs start at £9,500 ex VAT and typically take 8 to 12 weeks, covering discovery, UX, build, SQA testing, App Store launch and maintenance. It suits startups and businesses that want an app they fully own.
ProntX is an app development company in London that designs, builds, tests and launches iOS and Android apps for startups and growing businesses. We build both platforms from one codebase, start with a focused MVP from £9,500, and stay on to maintain and improve the app once real users arrive.
Why many app projects stall
Most apps that fail do not fail on code. They fail because the first version tried to do everything, nobody tested the idea with real users, or the app launched with bugs that earned one-star reviews in the first week. By the time the budget runs out there is a half-finished product and no evidence of what customers wanted.
How we reduce that risk
We start with a short discovery phase to define the smallest version of your app that proves the idea or solves the problem. We prototype the key screens and put them in front of users before writing production code. Then we build in two-week sprints with a working test build at the end of each one, so you always see progress on your own phone.
What we build
What kinds of mobile apps do we develop?
We build customer-facing apps, internal business tools and MVPs for new products. Most share the same needs: user accounts, a secure back end, payments or bookings, notifications and analytics.
Customers
Booking and ordering apps
Appointments, deliveries, memberships and loyalty schemes, with payments, reminders and push notifications that bring customers back.
Startups
MVPs and marketplaces
A focused first version of a new product, built to test demand with real users and give investors something they can download.
Operations
Internal and field apps
Job sheets, inspections, stock checks and timesheets for teams on the move, with offline mode and photo capture that syncs when signal returns.
Platforms
Companion apps for web products
A mobile app for an existing SaaS platform or customer portal, sharing the same back end and design system as your website.
AI
Apps with AI features
Assistants, smart search, document scanning and recommendations, built with our AI development team and designed with privacy in mind.
Admin
Dashboards and back ends
The admin panel, APIs and database behind the app, so your team can manage users, content and orders without a developer.
Technology
Should you build iOS and Android apps from one codebase?
For most business apps, yes. Cross-platform frameworks such as React Native and Flutter let us ship to both stores from one codebase, which typically lowers build and maintenance costs compared with two separate native apps.
React Native or Flutter
We choose between them based on your project. React Native fits well when you have a web product in React or want to share logic with a website. Flutter is a strong choice for highly custom, animated interfaces. Both produce real native apps that feel at home on iPhone and Android, with access to the camera, location, biometrics, payments and notifications.
When fully native makes sense
Some apps need native Swift or Kotlin: heavy augmented reality, advanced Bluetooth hardware integration or apps that depend on the newest platform features on launch day. If that applies to you, we will say so during discovery and explain the cost difference rather than forcing a framework that does not fit.
How we work
How does mobile app development work with ProntX?
Six stages: discovery, UX and prototyping, build sprints, quality assurance, store launch and ongoing maintenance. You see a working build on your phone throughout, not just at the end.
Stage 1
Discovery
Workshops on your users, goals and constraints. We agree the MVP feature list, technical approach, integrations and a dated plan with a fixed price.
Stage 2
UX and prototype
User flows, wireframes and a clickable prototype of the key journeys, tested with a handful of real users before build begins.
Stage 3
Build sprints
Two-week sprints with a demo and a TestFlight or internal Android build at the end of each, so you can try every feature as it lands.
Stage 4
QA and testing
Structured test plans, real device testing, regression checks and beta testing with your users before anything reaches the stores.
Stage 5
App Store launch
Store listings, screenshots, privacy labels and review submission for Apple and Google, handled in your own developer accounts.
Stage 6
Maintenance
OS updates, crash monitoring, security patches and a roadmap of improvements based on how people actually use the app.
Quality
Why does testing matter so much in app development?
Because app users are unforgiving. A crash on first open or a broken payment screen can sink your store rating before you have a chance to fix it, and app updates take time to pass store review.
ProntX has its roots in software quality assurance (SQA), so testing is planned from the first sprint rather than squeezed in before launch. Every feature has written acceptance criteria. We test on a range of real iPhones and Android devices at different screen sizes and OS versions, on slow and patchy connections, and with accessibility settings such as larger text and screen readers switched on.
- Test plans and acceptance criteria for every feature
- Real device testing across iOS and Android versions
- Automated tests for core logic and critical journeys
- Regression testing before every release
- Beta programme through TestFlight and Google Play testing tracks
- Crash and performance monitoring from day one
Pricing
How much does app development cost in the UK?
A ProntX app MVP starts at £9,500 ex VAT. Business apps with more features and integrations typically cost £20,000 to £60,000, and complex platforms are quoted after discovery. The main cost drivers are the number of screens, user roles, integrations and back-end logic.
| Type | Price (ex VAT) | Typical timeline | Usually includes |
|---|---|---|---|
| MVP | From £9,500 | Typically 8 to 12 weeks | Core user journey, accounts, simple back end and admin, analytics, iOS and Android launch |
| Business app | Typically £20,000 to £60,000 | Typically 3 to 6 months | Multiple user roles, payments, bookings, integrations with CRM or ERP, richer admin tools |
| Complex platform | Quote | Phased | Marketplaces, real-time features, hardware integration, high security or compliance needs |
Beyond the build, budget for hosting and third-party services such as maps, messaging or payments, Apple’s annual developer membership and Google’s one-off registration fee, plus ongoing maintenance. We list all of these in the proposal so the total cost of ownership is clear from the start.
If your budget is fixed, tell us the figure. We would rather shape a smaller first release that launches well than stretch a budget across features that end up half-finished. Discovery is priced separately when the scope is unclear, and its output (user flows, prototype, technical plan and a fixed build quote) is yours to keep even if you build elsewhere.
Mobile app MVP
from £9,500 one-off
iOS and Android from one codebase
What is includedAI chatbot or automation
from £2,500 one-off
Assistants and workflows trained on your data
What is includedWho we work with
Who uses our mobile app development services in the UK?
Three groups mostly: founders launching a new product, established businesses moving a process onto mobile, and companies adding an app to an existing website or platform.
Founders
Startups testing an idea
You need a credible first version quickly and on a fixed budget. We help you cut the feature list to what proves the idea, then build a roadmap for the next round of funding or revenue.
SMEs
Businesses going mobile
Service firms, retailers, clinics and trade businesses replacing paper forms, phone bookings or spreadsheets with an app their customers or staff will actually use.
Product teams
Companies extending a platform
You already have a web product and in-house developers, and need extra capacity or mobile expertise. We can work alongside your team, follow your code standards and hand over cleanly.
We work with clients across London and the rest of the UK, with workshops in person or by video. You keep a single point of contact who manages the project day to day. Whichever group you fall into, you get the same fixed-price phases, fortnightly demos and plain-English progress updates, so you never have to guess where the budget is going.
Ownership and trust
Who owns the app and the code?
You do. The source code, designs, store listings, developer accounts and data all belong to your business, and we are happy to sign an NDA before you share your idea.
- NDA available before discovery
- Full intellectual property transfer on payment
- Code in a repository you own, with documentation
- Apps published under your Apple and Google accounts
- UK GDPR considered in data storage and consent flows
- No holding code or accounts hostage
- No surprise licence fees from us
- No offshore handoffs without your knowledge
- No promises of downloads or chart positions
After launch
How do you get people to download and use the app?
Launch is where growth work begins. Because ProntX is also a marketing agency, the same team can plan your store listings, launch campaigns and onboarding emails.
We optimise store titles, descriptions and screenshots for the searches people use in the App Store and Google Play, and set up analytics events so you can see where new users drop out of onboarding. Small fixes to the first few screens often do more for retention than new features.
When you are ready to drive installs, our paid social and PPC teams run app campaigns, and a supporting landing page from our web design team gives search engines and AI assistants something to cite.
That is normal. Tell us the problem you want to solve through our contact page and we will reply within one working day with questions, a suggested MVP scope and a likely price range.
How it works
What happens after you get in touch
- 01Free audit
We review your site, search visibility, ads and competitors, then send a short video walkthrough with the quickest wins.
Request audit - 02Plan and price
A one-page plan with goals, channels, timeline and a fixed monthly price. No surprises later.
See prices - 03Launch in weeks
Tracking first, then quick wins, then the bigger builds. You see progress in the first month.
See our work - 04Report and grow
Monthly report in plain English: leads, sales, cost per result and what we do next.
Talk to us
FAQ
App development questions, answered
Still unsure? Ask us anything. We reply within one working day.
How much does it cost to build an app in the UK?
With ProntX, an app MVP starts at £9,500 ex VAT for iOS and Android from one codebase. Business apps with multiple user roles, payments and integrations typically cost £20,000 to £60,000. Complex platforms are quoted after a discovery phase. Ongoing costs include hosting, third-party services, store developer fees and maintenance, which we set out in the proposal.
How long does it take to develop a mobile app?
A typical MVP takes 8 to 12 weeks from discovery to store submission. Larger business apps typically take 3 to 6 months and are often released in phases. Apple and Google review new apps before publishing, which can add a few days. You get a dated sprint plan at the start and a working test build every two weeks.
Do you build for both iOS and Android?
Yes. We usually build both from one codebase using React Native or Flutter, which keeps costs down and means new features reach both platforms at the same time. If your app needs capabilities that only native Swift or Kotlin can deliver well, we will explain that during discovery along with the cost difference.
Will you sign an NDA?
Yes. We are happy to sign a mutual NDA before you share details of your idea, and our contracts assign full intellectual property in the code and designs to you on payment. Your app is published under your own Apple and Google developer accounts, and the code lives in a repository you own.
What is an MVP and do I need one?
An MVP (minimum viable product) is the smallest version of your app that solves the core problem for real users. It lets you test demand, gather feedback and show investors a working product before spending on every feature. Most new apps benefit from starting this way. Existing businesses digitising a known process can sometimes go straight to a fuller build.
How do you test apps before launch?
Testing runs throughout the project. Every feature has acceptance criteria, we test on a range of real iOS and Android devices, run automated tests on core logic, carry out regression testing before each release and run a beta with your users through TestFlight and Google Play testing tracks. Our team has a software quality assurance background, so this is a core part of how we work.
Do you maintain the app after launch?
Yes. Apps need regular updates for new iOS and Android versions, security patches and library upgrades, plus fixes for issues found in real use. We offer ongoing maintenance with crash monitoring and a planned roadmap of improvements. Because you own the code, you can also move maintenance to another team at any time.
Can you add AI features to my app?
Yes. We build features such as in-app assistants, smart search, document and receipt scanning, summaries and recommendations. We choose models and hosting with data privacy and UK GDPR in mind, and keep humans in control of sensitive actions. Our AI development service covers this in more detail.
Works well with
Related services
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