Just to touch on preparing yourself and your car, the trip is quite gruelling on the car, it's a lot of miles in a very short space of time so it's important to consider the following
Oil Level is good and checked throughout the weekend, bring a spare litre or so (or 5 if you drive a Honda
Brake/Steering/Clutch fluids are all up to standard
All tyres are in good condition, good thread depth with no rips tears
If the car is due a service shortly after the trip you might consider doing it beforehand
Make sure all bulbs are working, carry a few spares too
Try and have the car clean inside, it can be quite depressing sitting in a dirty car for a long period, it's ok on the 4 mile round trip to work but it will bug you on the longer trip
Last year Urban Per4mance offered a free safety check to every driver taking part, this won't be available this year
but I'll look into getting something sorted with another garage
I will be carrying a basic tool kit, trolley jack and diagnostics so hopefully that will cover everybody
As for preparing yourself, I have been dricing silly distances for years with my work and the most important thing is comfortable trousers/jeans/whatever. There's nothing worse than sitting for hours on end in an uncomfortable pair of jeans.
Plenty of water in the car, maybe get yourself a small ice box. Some high energy foods, protien bar etc. If you start feeling tired do not resort to any 'High Energy' drink, these will have you flying for 30 minutes and then you're worse off. The best thing to do is inform one of the organisers and we'll stop, get a rest and some food.
In the event of a breakdown you will not be left behind, last year we had two and both drivers got the cars safely onto recovery trucks and carried on as passengers
I'm sure I'll think of more to add to this