Any suggestions for waterproof jackets?

This subreddit must get a lot of posts like these, I'm very sorry to add to the pile, but I'm going insane trying to find a suitable, budget friendly rain jacket for hiking and camping. I've looked at over a dozen different forums and/or posts and everybody seems to be saying something slightly different, so I just have a couple questions.

I'm not planning anything crazy, but I'd like to be able to go on some hikes over he next few months in the UK while being confident knowing that in light and medium rain I'm going to stay dry. My budget is not that great, ideally no more than £100, and I was trying to look at secondhand jackets too to maximise my budget, although not sure if that's a good idea or not.

Once again, apologies for asking a question I imagine has been asked hundreds of times before this, but any help is really appreciated, thanks!