Auto 1 have the CAMS approved ones, I just got mine from there (My old one expired)
What you need...
make sure car is in good heathly order.
no leaks etc
top fluids up if need be.
bleed brakes if you can.
when you get there - take every lose item out of the car. including boot
wear long sleeved shirt and pants and covered shoes
ADR aprooved helmet
If you are on street tyres, they will cop a beating depending on how hard you go. If you are relatively new to it, dont go as hard!
I have my semi's and road tyres so I have spares
when your out there...
first couple laps, warm up car tyres etc etc
go for a few laps, then do a cool down lap. when you come back to pits, do a few laps again of the car park just too keep it again.
come into pits, leave it on a flat surface and dont put on handbrake
dont have a big night before hand! (I ALWAYS make this mistake) and before each session, go to the toilet.
bring plenty of water and food