Physically, your local "Cash Converters" or similar may be worth looking at, depending on how you feel about them and that type of business.

Digitally, there's places that do refurbished laptops, for example Laptops Direct have a refurbished section which I've used before on behalf of other people : laptopsdirect.co.uk.

£200 may be a struggle, but under £300 should get you something that'll definitely do the job.

Depending on what you're doing, Operating System may be an issue if you want Windows, as they've stopped updating 10, and 11 won't run on older machines. If you want Linux, you're fine. Do a quick Internet search for the laptop model & "Linux" to check if there's any issues i.e. a weird WiFi card etc.

Double check with a nerd before you click "buy" (asking a follow up question on here should work).