FUNNYPERSON
" is worth it ringing up the faculty admissions co ordinator with the name of a small,poor,but pleasant college for a third interview should they be considering such a thing."
I don't often post - but this is such a large piece of misinformation I feel obliged too.
I can only speak for Oxford but I honestly think this is such an outdated piece of advice.
Oxford admissions are, in some sense, quite centralised now in terms of candidates having further interviews at other colleges.
Some people will be reinterviewed because the original college had a lot of good applicants, and feel that this person meets the grade but they don't have the space so offer them to another college who perhaps had a lower standard of applicants.
Some will be reinterviewed to even up applicants across all colleges - sometimes there are years when a course at one college can be oversubscribed and undersubscribed at another, so applicants are moved or reinterviewed at the second college.
It's not an exact science - but tutors know what they are doing.
Colleges work together to try and ensure across all colleges that applicants are comparable, so that the best get places. The aim, and what they try and say, is that it doesn't matter what college you apply to. If you are good enough, you will get a place somewhere. Obviously this isn't flawless, and people do slip through, but in my experience Oxford is committed to getting the best.
I don't see how ringing a college and requesting an interview will fit into this practice. Oxford try VERY hard to ensure the best get a place, which is why people are reallocated. In 2012 25% of successful applicants received an offer from a different college to the one they applied to.
College Choice
This link shows some of the statistics about college choice. There's a wealth of data on the Oxford website that quashes a lot of myths.
As I said, I cannot speak for Cambridge. Their pooling works differently, as there's a delay (until after Xmas I believe) for interviews at 2nd colleges.
If you're reinterviewed at Oxford, it will be when you are there for your first interview.