I'm afraid this might not answer all your questions, but I'll do my best anyway! Being a music student I spent most of Fresher's week rehearsing for the concert on the Sunday at the end of the week. This wasn't actually boring or anything - in fact it was a great way to meet other people.
Basicly there's mostly events at the union. The first night party is called appropriatly enough First Night Nerves. Again, this was mostly meeting other people (most of whom I've never spoken to again, but still). After that there are other events, sports tournaments, hall pub crawls, etc.
One importanat thing: Make sure you get down to campus fairly early to get your RCS Card (so you can pay for stuff) and your UoL card (so you can get into the union) and various other things, as the queues can get pretty bad after a while. While you're there you will probably get people from hundreds of societies trying to get you to join theirs...