(Original post by Noble.)
Firstly, you'll find just as many private school kids at Imperial I imagine, however, you're probably talking about the stereotypical stuck-up toffs, because you can't instantly tell everyone who went to a private school, and you're going to get those at every University.
Don't feel like it's pretentious to have unconditionals for both, if you've got your grades... you've got your grades, you're going to get an unconditional. As for wanting to live field-free... you're not going to find fields in the centre of Oxford despite Oxfordshire being somewhat full of them. Having friends going to Imperial definitely shouldn't sway your decision, it's totally irrelevant, it's your education, and chances are, you'll find yourself with a completely different set of friends after a while anyway. As for wanting to cook, you can live out (or choose alternative Uni accommodation) in your second year; you can actually live out first year if you want, but need permission from the dean to do so, but picking to do this purely because you like cooking is a bit stupid, so I wouldn't recommend it. However, you're going to be in college for an 8-week term, then you go home for 6-8 weeks, where you can cook. Those 8-week terms fly-by, without question.
I imagine Oxford sent a reading list because the vast majority of those given an offer will accept the offer, and besides, the reading list is going to be helpful even if you were off to study Chemistry in China, so they're hardly doing students not picking Oxford a dis-service by sending them it.
I can tell you one big anti-London point - money. Oxford has some of the best funding of all UK universities, and if you live in college, some of the cheapest accommodation and catering. You're going to find the polar opposite of this in London, your student income will be lower (I doubt Imperial has bursaries/funding to rival Oxford/Cambridge) and your rent is probably going to be 3 fold that of Oxford.
You seem to be hung up on a lot of misconceptions regarding Oxford, and drawn towards Imperial (London) for the wrong reasons. The point of going to University (when you're talking about Universities in the leagues of Oxford and Imperial) is to study the subject, and that's really what should account for the majority of the decision.