Is there anything that you wish someone had told you before your interview?

Well, first of all, "calm down"! There really is no need to be overly nervous; an interview is essentially a conversation between you and someone who loves your subject every bit as much as you do. It will be challenging, but it can also be fun (albeit, in a way that might make your head hurt a bit). There is no need to panic about saying the wrong thing or getting the wrong answer. Your interviewers aren't checking to see if you're the fountain of all knowledge; they just want to see how you think and how you might cope with the kind of teaching Oxbridge prefers. If you need to think for a bit or ask for clarification from your interviewers, that's fine! It won't reflect poorly on you and your interviewers will try to help you as much as they can, so try not to be too stressed about answering everything 100% correctly every time. Also, there's no such thing as an "Oxbridge person". Speaking or dressing in a particular way will not help or hinder your chances (well, within reason...going for your interview in fancy dress is not advisable by any stretch of the imagination). You do not have to come to your Oxbridge interview dressed for a job interview. Feel free to see if the college you've applied to has any guidelines on what to wear, but, generally speaking, you should wear what you feel most comfortable in. I wish someone had told me that before I rocked up looking like some sort of boardroom exec/awkward adolescent penguin hybrid.