Mobile App Development Guide for UK Startups: Costs and the Process

Step-by-Step App Development Process

1. Idea Validation

Every app should solve a real, validated problem. To test your idea:

• Conduct user interviews to understand pain points
• Create a one-page landing site (using Carrd or Webflow) and track sign-ups
• Use Google Trends or AnswerThePublic to measure interest

Early validation helps avoid building the wrong product.

2. MVP Planning

An MVP (Minimum Viable Product) is the fastest, simplest version of your app that still delivers value.

Steps to follow:

• Prioritise core features only
• Sketch the user journey (use Miro or Whimsical)
• Decide what to launch with, and what to defer

Starting small lets you test real usage before scaling.

3. UI/UX Design - Tools & Approach

Clean interface and frictionless experience can make or break your app. Good design helps users trust and understand your product.

We recommend a few different tools to help with ui ux design, some of our favourites include, Figma for collaborative UI design and prototyping. Mazefor user testing interactive prototypes, and Miro for brainstorming, mapping user flows, and wireframes.

Design Process Summary:

• Wireframing: Define structure before visuals.
• Prototyping: Test clickable flows.
• Visual Design: Apply your brand, colours, and components.
• User Testing: Identify bottlenecks before development.

Accessible, intuitive UI is more important than flashy visuals. Prioritise usability.

4. Development: Frameworks, Frontend & Backend

There are 2 main components to consider when building a mobile app: Frontend and the Backend . You also have hidden variables like hosting to consider, but we will cover that later.

Frontend: This is what your users see and interact with. It is essential that your frontend's UI fits your brand and most importantly, it doesn't break the UX.

• React Native it is a JavaScript framework by Meta that allows developers to build apps for both iOS and Android using a single codebase. It’s ideal for most MVPs. It uses common web coding patterns and tools. To use it, you need Node.js, npm , a code editor like VS Code, and a mobile emulator or device for testing
• Flutter is Google’s UI toolkit using the Dart language. Offers high performance rendering and excellent custom UI. It is great if you need animations or custom graphics.
• Swift UI is Apples native UI framework. It is used to build app interfaces for Apple devices. It lets you design the app’s layout and behavior using a simple , code-based approach that shows instant visual results.

Backend: This is the most important part of developing an app and often downplayed, you depend on tools such as NodeJs , Spring Boot and Ruby on Rails , to handle what happens behind the scenes in your app, like saving user data, processing payments, or managing logins.

• Node.Js lets you develop the backend of your app using JavaScript, the same language you use for frontend web development. It runs code on the server side, you can handle things like user requests, database actions, and app logic.
• Ruby on Rails lets the user build backend systems that can handle everything from storing data to handling user sessions. If you are already comfortable with Ruby, this is your go to in order to create full-featured web applications quickly, with less code and more built-in functions.
• Spring Boot is a backend framework built on top of Spring, it helps you create web services and APIs for complex applications. You use it to handle the logic, data processing, and communication that happen behind your app’s interface.

5. Testing & Launch

Don’t skip testing. Even small bugs can ruin trust and the user experience. Many freelancers and agencies will skip this step in mobile app development, but it is essential to ensure your app is ready for the public.

You may have heard of the term QA or Quality Assurance, this is the process of testing your app to ensure it works as intended. You can do this manually or use automated testing tools. But the main thing is to test for:

• Functionality: Every button and flow should work.
• Cross-device: Test on multiple screen sizes and OS versions.
• Performance: Ensure fast load times and smooth scrolling.
• Security: Encrypt sensitive data, use HTTPS, and test auth flows.

After all tests pass and you are happy, you can submit your app to the Apple App Store and Google Play Store. Be sure to use tools like TestFlight (iOS) and Google Play Console (Android) to share beta versions.

6. Cost to Build a Mobile App in the UK (2025)

The cost of building a mobile app in the UK varies widely based on complexity, features, and the team you choose. a breakdown of typical costs:

Prices depend on feature complexity, integrations, platform(s), and testing requirements. MVP-first approaches are the most budget-friendly for startups. It is never a good idea to build a full-featured app without testing the market first. To learn more about how you can test your app idea, check out our how to validate your startup idea blog post.

7. Cross-Platform vs Native App Development:

There are many factors to consider when choosing between cross-platform and native app development. Here is a table that compares the two approaches:

For most startups, cross-platform gives the best mix of speed, cost-efficiency, and user experience. However, if your app requires heavy graphics or platform-specific features, native may be worth the investment, but that is a choice you will have to make with your team.

8. Should You Build an MVP First?

Yes. MVP development reduces time-to-market, lowers risk, and helps you learn from real users. You don’t need to launch with every feature. Build small, ship fast, and iterate.

Generally, startups and small businesses that launch an MVP first:

• Spend less upfront
• Adjust direction based on feedback
• Show early traction to investors

After launch, you are then able to gather real user feedback, which can help you make informed decisions about what features to build next. This iterative approach is key to successful app development.

Choosing a Development Agency or Going Solo/freelancer

You can build solo, hire freelancers, or work with a development partner. Each has its pros and cons.

If you decided to hire a freelancer, you can expect the following pros and cons:

• Easy to manage since you are only dealing with one person
• Best for founders with technical experience
• Can sometimes be cost effective, unless you end up doing a lot of revisons(which is common with freelancers)
• Limited Resources, you are relying on one person to do everything, which can be a bottleneck.

If you decided to go with a development agency like Peachr, you can expect the following:

• More experience/specialities. Enjoy the peace of mind that your working with the best in the industry.
• Affordable pricing options such as 0% APR payment plan.
• Highly dependable since they have a repuation to maintain.
• More secure and confidential. The mobile app development agency will have different protocols to follow to protect their clients