Maths at Warwick or Oxford

Cambridge certainly care about the personal statement although of course they would be mostly interested in the stuff that relates to maths. It wouldn't have to be spectacular - things such as a bronze maths challenge performance or mentioning a book you read are useful to them.

For Warwick, yes, they would probably not pay as much attention given their standard offer. I don't know as much about Oxford and Imperial but it's likely that they would be interested in the personal statement.

oxford, warwick is a boring dive with nothing to do as an area

Define 'care'. Unless someone has solved Riemann's Hypothesis in the PS. or has sworn in it, I'm not sure it would ever sway an admissions decision.*

*I'm ignoring putting in things like doing well in BMO1/2, which do go into the PS, but then they're tangible achievements and there really should be other places to be able to put things like that.

I'm basing this on feedback I received when I applied a few years ago. They acknowledged things like books I mentioned (only the ones I talked about at length, not the ones I just listed), maths challenge etc. Probably also UMS marks but I can't remember exactly what they said. Based on that, they put me in their top group of candidates prior to interviewing me. Then they interviewed me and I didn't really handle the questions that well and I was rejected.

Hey! I live in Warwick!

...yeah, you're probably right.

Except that Warwick (university) is not in, or even particularly near to Warwick (town).

I live on the outskirts of Warwick, it's a 15-minute drive. Plus the area around warwick uni is basically as dead as warwick itself

"Dead" isn't the word I'd use. "A hideous derelict council estate" would be more accurate. Warwick is nice.