I meant reasonably well on each individual interview; obviously I was over the moon to have so much choice in where to go! I firmed Oxford back in May and found out the week before last that I've got my grades, so I start there at the end of the month
I'd definitely say double, triple then quadruple check that your phone is off... Don't be afraid to take a few seconds to think before answering the interviewers' questions, and take your time when speaking as well. Obviously don't go overboard with this, but being able to think as you speak helps stop you from talking nonsense and allows you to think as you're speaking.
Don't necessarily view it as a bad thing if you get interrupted or if you feel like you're being interrogated - they're short on time and are just trying to get as much out of you as they can. Even before the phone incident I felt like my Newcastle interview was a horror show, as they cut me short halfway through what I'd thought was a really good anecdote about how my volunteering had strengthened my resolve to do medicine, and at the time I was worried they just weren't interested, but they have a strict schedule to keep to. They also kept asking tricky follow up questions to the standard "Why do you want to do medicine?" question they asked at the start, which made me think I was giving bad answers, but I guess they were just trying to get to the root of my motivations and seeing how I coped under pressure.
I just used this book:
http://www.amazon.co.uk/gp/aw/d/1905812051?pc_redir=1408122732&robot_redir=1which was pretty good. Definitely get a practice interview from someone who knows that they're doing if you can (and get them to be as mean as possible), because I didn't and, although it didn't matter in the end, I still think it would have helped. If you're applying for Oxbridge, UCL or Imperial, read over everything you've done at AS and so far in A2, because it'll really help in the science-based questions they ask. Read plenty of articles about recent or major historical medical developments too, because I imagine that'd have helped in my Oxford interview... I didn't really do enough of that, and was very lucky that I got asked a lot about the two things I'm most interested in.
If you want to ask anything else, feel free