I'm not actually at Oxford, but I've got a deferred place at Christ Church.
I think anyone who goes on these forums regularly will know to take the college stereotypes with a pinch of salt, and I wasn't going to bother commenting, until I noticed someone had said ChCh looked 'too grand' for them. I've now been up there three times (two open days and interviews) and I've yet to encounter any of the stereotypes! Yes, I can see the 'grand' architecture putting some people off...but don't rule it out on any crazy social issues. It's one of the colleges that's putting a hell of a lot of effort into access, it's 50:50 private/state, and Brideshead was a long time ago!
Sorry if this sounds like a bit of a rant! But I'm definitely not from a "posh" background and my experience of the college and its students so far have been really great. So don't discount ChCh, or any other college, on anecdotes!