@Sammy H
Theres only about 20 mins difference between the 2, so seeing as I've been down south before, figured I go where I'm more familiar.
@DJ1425
There is a little preparation you can do. Practice your interview technique!! They'll ask about times where you've gone wrong with something, and what you did (e.g. did you get flustered/work through it/learn from it etc), and they'll also ask for examples of when you've been been successful at something, responsible, creative etc. Its an in-depth interview, mine lasted just over an hour. However, dont worry about if you've said enough, if they want more info from you, they ask questions to guide you, so they'll get all they need.
As for the group exercise, you can't really prepare. They'll set you a task on the day to complete whilst they observe you. You've just got to bounce off the grou you're in, and try to speak up without taking over.
Hope this helps,
binbrain