I've had all 3 Saff escort and focus Rs all within your budget

Saff: will appreciate if you get a nice one, plenty of tuning potential, high running costs, paranoia is high

Escort: will get an minter for £5k guaranteed appreciation, rust problems, don't drive we'll, parts are cheap, feels like a ford RS should

Focus: values are all over the place £5k-15k. You get what you pay for, mine was 1 owner and has been uber reliable, just sits in the garage, take it out on a sunny day, super reliable, and really is a quick car after a few mods

My money would be on a focus but don't expect to run it on the cheap, look at lots, don't just buy the first one. £8k should get you a 70-80k miler. Personally id buy a modified one, as it saves money, but only if your confident the previous owner has looked after it.