Hey mate, dont worry at all about it. It is a thorougly enjoyable day. My interviewers were very nice, and there is a very friendly aptmosphere. My advice would be to do some homework, especially on st georges. Keep calm and confident, DONT LET NERVES GET THE BETTER OF YOU. I have heard that this is a big thing at st georges, i firmly believe my interview went spiffingly simply becuase i was calm and confident. Also be talkative during the day, as apparently the students report back on you (remember the 'conduct throught the day' bit of the letter?).
All the best.