I think you'd be better of going for York based on everything you've told me, since, it's seems like Warwick's rep is possibly the only thing making this a difficult decision. I think Warwick does have alot more going on than York though, and you said that you were worried about being bored, esp being from London. I think in terms of general prestige, Warwick has quite abit on York, esp in certain career industries, but that's not too important.
That's fair enough, you seem to prefer the York course by a country mile. I'm sure Warwick's EPAIS focuses alot on politicial theory and the likes of Hobbs, which is closely entwined with political philosophy. The Warwick course does seem to have aspects of political philosophy, and has a year in the US if that interests you. I'd say if the content of York appeals to you, go with that, but it's not unheard of for students, to hate the things that they thought they would love, and love the things they thought they'd hate, so don't rule it out just yet.
Your AS grades aren't bad, I've seen people get Politics/IR offers from Warwick with similar. Your predicted grades are fine, and applying through the access scheme would only help. I'm guessing, but it seems like you have AAA, AAB, AAB ? and then another AAB? I'd probably say York would suit you more, but Warwick does have the pubs, you may just not have discovered them
but sadly the course content doesn't cater to your needs.