i'm in a vaguely similar boat (although with another subject), but almost as soon as the oxbridge rejection came through, and i more to an extent when all 6 unis had replied, i knew that whether i decided to apply again or not i'd have to really look at my firm choice uni. with the prospect of reapplication, and even failure at reapplying, i made the decision to "become" passionate about the place i was most likely to be going. it's a bit of a weird thing to say i guess, but rather than browsing the oxford college websites and daydreaming into the computer screen, i found as much out about my course at my new uni as possible, went up there to visit for the day, thought about the various modules they offer which appeal to me etc.
i'll admit that i'm still considering reapplying, but i know that going to my current firm choice university would be just fine, and a really good experience. although it's possible for me to end up with the necessary 3As at A level, and perhaps a desireable aea mark (plus a wider reading, knowledge and understanding compared to when i first applied), i've got a similar bunch of gcse results and i suspect that they might always be a factor in making an application slightly harder.
another thing though is that wherever you study, you'll have access to the same wealth of books (maybe applies more for my subject, english, though) and general writings. come university i get the feeling that there's a great element of self-teaching which might be needed. furthermore, if people do have the deep interests, great passions and lifetime fascinations about the subject of which they talk about in their personal statement, then they should be able to excel at their chosen subject at pretty much whatever uni. teaching and facilities might be marginally better at oxbridge, but there should be nothing in the way to prevent someone who is really into their subject from putting in 3 years of hard work and enthusiasm, to come out with a respectable degree elsewhere.