There is no single best AI assistant for a UK firm of 15 to 150 people. The useful question is which one fits the way your team already works. If your files, email and calendar sit in Microsoft 365, Copilot is the obvious one to trial first. If you run Google Workspace, or a mixture, ChatGPT Business or Claude Team usually fits better. This guide covers what each offers, what each costs at the time of writing, how they handle your data, and a simple way to choose.
A note on prices before we start. Every figure below is the UK price shown on the company’s own page at the time of writing, and each page shows prices for your country, so check yours: Microsoft, ChatGPT and Claude. Plans, names and prices in this market change often. If a detail here has moved by the time you read it, the official page wins.
One disclosure. We are rolling out Claude with training for a construction firm in Hertfordshire, alongside ongoing technical support, so Claude is the one we know best in practice. Everything in this comparison is taken from each company’s own pages, not from that experience.
Microsoft 365 Copilot Business
Microsoft sells this as an add-on to an eligible Microsoft 365 Business plan, for firms with up to 300 users.
Price. At the time of writing, Microsoft’s UK page shows a list price of £16.10 per user per month on an annual subscription, excluding VAT, on top of your Microsoft 365 plan. Microsoft is running an introductory £13.80 for the first year on offers placed between 1 July and 31 December 2026.
What it is good at. It works inside Word, Excel, PowerPoint, Outlook and Teams, and it can draw on your own emails, files and meetings. Microsoft says it respects your identity model and permissions, so each person sees answers built from what they can already open. If your firm lives in Outlook, Teams and SharePoint, that is the strongest argument for it.
Worth knowing. Because it works within existing permissions, anything a person can open, Copilot can draw on for them. That is our reading rather than a Microsoft warning, but it means tidying messy SharePoint permissions before you roll it out. Also check what you already have: Microsoft says web-based Copilot Chat is included at no extra cost with an eligible Microsoft 365 subscription, so your team may be able to try a version of Copilot before you pay for the add-on.
Admin. Copilot is managed from the Microsoft 365 admin centre. Microsoft’s documentation lists Copilot controls for who can use it, whether it can search the web and who can create agents, plus usage reports and a dedicated AI Administrator role. If someone already looks after your Microsoft 365 tenant, this is the least new to learn.
Fit. Best on Microsoft 365. It requires a Microsoft 365 subscription, so on Google Workspace it is not an option on its own.
ChatGPT Business
This is a standalone workspace rather than an add-on to something else.
Price. At the time of writing OpenAI’s UK page shows £15 per user per month billed annually, or £18 per user per month billed monthly, for two or more users. The page does not say whether VAT is included, so confirm at checkout.
What it is good at. OpenAI lists chat, ChatGPT Work and Codex (its coding tool), connections to tools including Microsoft 365, Google Drive and Slack, and company knowledge and custom team agent plugins. It is a general-purpose assistant that is not tied to one office suite.
Admin. The page lists central billing and administration, usage analytics, budgeting and spend controls, and SAML single sign-on with multi-factor authentication. Data residency in ten regions, including the UK, is listed under Enterprise, which is custom-priced, not Business.
Fit. Good on Google Workspace, or on Microsoft 365 if you want a standalone assistant that also connects to it.
Claude Team
Anthropic’s Team plan is also a standalone workspace, for teams of 2 to 150 seats.
Price. At the time of writing Claude’s UK page shows a standard seat at £18 per seat per month billed annually, or £22.50 billed monthly. The page says prices include 20% VAT, which makes the annual standard seat £15 before VAT (our arithmetic). A premium seat with five times the usage is £90 billed annually.
What it is good at. The standard seat includes all Claude features, shared projects, Claude Code and Cowork, enterprise search across your organisation, and connectors for Microsoft 365 and for Google Workspace. On Team, an organisation owner has to enable the Google Workspace connectors before individuals can use them. The 150 seat limit covers almost everyone in the range this guide is written for.
Admin. Central billing and administration, single sign-on, admin controls for connectors, and usage analytics. Audit logs, SCIM provisioning and custom data retention controls are Enterprise features, not Team.
Fit. Good on either Microsoft 365 or Google Workspace, as a standalone assistant.
Data protection on business tiers
On the business plans, all three companies say your content is not used for model training by default. Microsoft says prompts, responses and data accessed through Microsoft Graph are not used to train foundation models, and that use is covered by its Data Protection Addendum with Microsoft acting as processor. The ChatGPT and Claude pages each state no training on business data by default.
Three cautions. First, the protection attaches to the business plan and a work sign-in, not to the brand. Microsoft’s terms apply when staff sign in with their work account, and a personal ChatGPT or Claude login does not carry the business-tier terms. Second, web searches made by Copilot go to Bing under separate terms, which Microsoft documents. Third, read the data processing agreement for whichever you pick instead of relying on a pricing page.
Our guide to where your data goes when you use ChatGPT and Claude goes through the tiers in detail. Whichever tool you choose, write down what staff may and may not put into it. Our one-page AI policy template is a starting point.
What it adds up to for 40 people
Here is the arithmetic for a firm of 40 where everyone gets a seat, using the prices above on annual billing. This is our own calculation from the published figures, so treat it as a guide, not a quote, and check the current price on each official page before you budget.
- Copilot Business: 40 seats at £13.80 is £552 a month in the first year under the introductory offer, or £644 at the £16.10 list price, excluding VAT, on top of what you already pay for Microsoft 365.
- ChatGPT Business: 40 seats at £15 is £600 a month, with VAT treatment unconfirmed on the page.
- Claude Team: 40 standard seats at £18 is £720 a month including VAT, which is £600 before VAT.
The three land closer together than the headline prices suggest, so cost is rarely what decides it. You also do not have to buy 40 seats on day one. Starting with the five to ten people who will use it hardest is a sensible way to test, as long as you check each vendor’s terms for adding seats later.
A simple way to choose
Start with where your work lives, then let a trial decide between the realistic options.
| If this describes your firm | Start by trialling |
|---|---|
| Work lives in Outlook, Teams, SharePoint and Office on a Microsoft 365 Business plan | Copilot first, plus one standalone tool for comparison |
| Google Workspace, with Gmail and Drive at the centre | ChatGPT Business and Claude Team |
| A mixed estate, some Microsoft and some Google | ChatGPT Business and Claude Team, with Copilot only for staff who live in the Office apps |
| You need audit logs, SCIM provisioning, custom data retention, or UK data residency (listed for ChatGPT Enterprise) | The Enterprise tiers, which are priced differently |
| More than 150 people, or more than 300 | Check seat limits first: Claude Team stops at 150 seats and Copilot Business at 300 users |
Then run this process:
- Pick five real tasks. For example: summarising a long supplier contract, drafting a tender response, turning meeting notes into actions, building a first-pass cost comparison in a spreadsheet, answering a tricky customer email.
- Trial two tools for two weeks. Give each to the same small group of five to ten people, doing the same five tasks, and ask them to note which they reach for.
- Check the boring parts. Data processing agreement, who administers accounts, single sign-on, what usage reporting you get, and what happens to your data if you cancel.
- Decide, then write the rules. One approved tool per person, personal accounts off limits for company data.
- Roll it out with training. Training is what turns a licence into something people actually use. Our 30 day plan for rolling out ChatGPT or Claude covers the first month.
None of the three wins for every firm, and the models underneath all of them change regularly, so the comparison that matters is the one you run on your own work. If you would like a second pair of eyes on it, the Systems and AI Review is half a day with us, on site or on a call. You get a two page plan covering the three places your admin costs you most and what to fix first, and a fixed quote for the next step. You can also book a 30 minute call first.