A £20-a-month AI tool beats a custom build when one person starts the task, the inputs change each time, and someone checks the result anyway. A custom build wins when the same job runs many times a day, needs to follow your rules every time, or has to move information between your systems without anyone copying and pasting.
Most businesses start with ready-made tools, and that’s sensible. Of UK businesses using AI for language tasks such as writing and chatbots, 71% bought external software, 14% built their own and 9% outsourced the build (DSIT, AI Adoption Research).
Full disclosure: AI Business Systems builds custom AI tools, and this guide will sometimes tell you not to buy one. Prices change often: these were correct at the time of writing (October 2026).
What a £20 tool can do for you now
At the time of writing (October 2026):
- ChatGPT Plus: $20 a month (OpenAI)
- Claude Pro: $20 a month, or $17 a month billed annually (Anthropic)
- Microsoft 365 Copilot Chat: “available at no additional cost” with an eligible Microsoft 365 subscription. It answers from the web; working with your own files and email needs a paid Microsoft 365 Copilot licence (Microsoft)
- Gemini in Google Workspace: included in Business plans, from £5.90 per user a month excluding VAT (Google)
You might already be paying for one of these.
They’re good at jobs where you’re in the loop: drafting emails and proposals, summarising documents and meetings, rewriting copy, researching a question, brainstorming, and making sense of a spreadsheet you upload.
One caution: individual plans are made for individuals. If you’ll paste in customer data, use a business plan with data processing terms. Our guide to using AI with customer data explains why.
Where a £20 tool falls short
- Volume. Someone has to paste every input in and copy every output out. Fine five times a day. Painful fifty times.
- Moving information between systems. A chat assistant won’t update your CRM, raise an invoice and email the customer in one go.
- Working without you. It can’t start itself when an enquiry arrives at 9pm.
- Consistency. Different people get different results from the same tool. Your rules and formats aren’t applied every time unless someone remembers to ask.
- Customer-facing work. A chatbot on your website, answering from your own information and handing over to a person, is a build, not a subscription.
The five-question test
| Question | If yes | If no |
|---|---|---|
| Does a person start the task each time? | Tool | Build |
| Does it happen only a handful of times a day? | Tool | Build |
| Will someone check every result anyway? | Tool | Build |
| Can it work without touching your other systems? | Tool | Build |
| Can the rules or format vary a little each time? | Tool | Build |
Mostly “Tool”? Set up a £20 tool properly before spending more. Mostly “Build”? A custom build will probably pay for itself. Our guide to what AI implementation costs shows how to check.
The middle option: set the tool up properly
Before you pay for a build, get more from the tool you have:
- Save your instructions. Most AI assistants now let you save standing instructions and reference documents for a task, so you don’t start from scratch each time.
- Build a prompt library. Write your best instructions down once and share them with the team, so everyone gets consistent results.
- Add your own material. Give it your price list, tone of voice and FAQs.
- Connect one or two simple steps. A low-cost automation platform can pass an email or form into the tool and the result back out. It’s a small step towards a build, without a big spend.
Worked example: replying to enquiries
Five enquiries a day. You paste each one into an AI assistant with a saved instruction and your price list, check the draft and send it. That’s a few minutes each, for the cost of your subscription. The tool wins.
Sixty enquiries a day from your website form. An automation reads each one, drafts a reply in your style from your price list, logs it in your CRM, and waits for your approval. You review and send in seconds, and nothing gets missed overnight. The build wins.
Signs you’ve outgrown the tool
- You or your team spend real time copying and pasting between the tool and other systems
- Two people get noticeably different answers to the same task
- Things fall through the cracks out of hours
- Customer data is being pasted into personal AI accounts
Next steps
Not sure which side your jobs fall on? The £197 AI Quick Start gives you a one-page plan saying which jobs need a tool and which need a build. If a tool is the answer, AI training sets it up properly for your team. If it’s a build, see custom AI tools.