Originally posted by Nippy
To study at you need to be of a certain 'calibre' as they put it, that basically means you need to have grades and talent and a glowing reference.
If you have these, then generally you need a lot of money. Terms at these schools cost a hell of a lot of money and generally only those with a 'private' school background get in. The entrance rate of public school students is still ridiculously low. If you have talent and grades they may consider putting you on a scholarship, it all depends on luck...
I think you're being a little unfair, here.
If you want to study at Oxford or Cambridge, top grades (usually including A-levels in or related to the subject you're applying for - for example, to study Physics, you need both Maths and Physics A-level; for Medicine you need Biology and probably another science; for Law it would be more flexible, but usually at least one humanities subject) and evidence of worthwhile extra-curricular activities will get you an interview. This is really where the decisions are made for Oxbridge, because on paper there's very little to differentiate the candidates. And this is where private schools do better, because their candidates are far better prepared for interview than those from state schools (I'm not using the term "public school" because it doesn't actually mean that in this country). The interview process has been criticised for its bias towards private school students, and Oxbridge have made effort in recent years to address this. (An additional problem is that pupils at state schools may receive less encouragement to apply to Oxbridge in the first place, whereas at a private school, all students with the necessary grades are probably encouraged to apply.) Oxbridge is making an effort to widen the scope of its intake. But it's difficult to suggest how else they can select their students other than some kind of interviews.
(Edit: I forgot as well, for some subjects - I know maths is one, not sure about others - you have to sit an exam called the STEP paper, which is notoriously (and deliberately), horribly difficult.)
Offers of university places are
not made on the basis of how much money a student has. (Although the old boys network may have a little influence.) IIRC the university doesn't receive details of how much money you have. Whatever university you go to, you can get a loan to cover the cost of your education, after the offer of a place is confirmed. The loan is means-tested, so if your family is poor, more money will be available to you. At Oxbridge there are more scholarships and grants available than most other UK universities because they're richer - and it usually depends on which college you apply to, some are richer than others.
If anything has discouraged poorer students from going into higher education, it has to be the introduction of tuition fees several years ago. Students are leaving university with massive debts. The National Union of Students is still holding rallies to protest against tuition fees, with little success. (Last year the students at my university held a particularly ill-planned protest, IMO - they (or at least those who knew it was happening and thought it might made a difference) staged a strike, and didn't go to lectures for a day. I can't see that this would have had any effect on the university at all - all it achieved was to deprive the students who took part of the education they're paying for...

)
Edit: And Robnark is sadly right about the old boys' network being important, although it does depend on career. Oxbridge generally aren't the top universities for less traditional subjects.