Biggles and others, congrats on getting through stage 2.
As for stage 3 tips just go there and be yourself. As interview preparation, try to think of any and all questions they might ask and think what you might say in response. A useful starting point for this is the link on this thread to the kent uni website (think is 5 or more pages back).
As for stage 4, there is nothing you can do to prepare really, just go in there and try your best - it's actually quite fun if you manage to relax!!
Best of luck guys n gals
Rod