it's probably easiest to keep an eye on
https://www.hotukdeals.com/
inevitability someone will post a deal for a good value/cheap laptop from dell or ebuyer (that's where I'd start browsing to get an idea what you can get for your money) etc, someone will say "that laptops rubbish as it's £300 and won't play the latest games" there will be some debate on how for £300 it's fine for browsing and not much else, which sounds like it's fine for your needs, and someone may post a link to a better value for money machine
that's what I did when I bought an HP for my missus several years ago, spent about £300 from ebuyer, still is fine for email, web browsing, spotify, you tube etc.
I'd also avoid Currys/pcworld, in the past they've had £600 machines reduced to £300 - so a half price computer is tempting, but it's an old model, and it's very possible this year's £300 is better than last year's £600.
Dell Outlet is also a good place to look.