If it was me (being both impecunious and naturally stingy anyway) I'd be looking for a refurbished laptop from a trustworthy company, so this is where I'd start:
https://www.accomputerwarehouse.com/cheap-refurbished-laptops-uk
From those models, I'd probably be most tempted by the Samsung 400B (with its solid state drive) or by the Dell Latitude E5440 (with an impressive 8Gb of RAM). If you're prepared to consider a refurbished model though, remember to add on bit more money (perhaps twenty quid or so) for a new battery; the batteries in refurbished laptops don't always hold a charge for very long.
If you're determined to buy new, my first piece of advice would be to avoid any of the ultra-cheap models which only have 32Gb of space on their drives. There have been lots of reports of people finding that Windows 10 can't update itself on such models due to lack of drive space. My second piece of advice would be to steer well clear of Chromebooks. (They're designed on the assumption that you'll do almost everything in the cloud, which might not suit your requirements).
Beyond that though, I'd be looking through the recommendations here to see which model best suited my needs:
https://www.techadvisor.co.uk/test-centre/laptop/best-budget-laptop-3214583/