To drive in Germany, you'll need a hi-vis jacket in the car, as well as a warning triangle, and a complete spare bulb kit, you also should have all your documents with you, the V5, MOT, insurance cert, and your driving licence at all times (even on the ring)
You should use headlight deflectors, but I havn't bothered the last 2 times I've been over there, I just adjust my headlights downwards if driving at night over there. If you've got HID's, you can also use tape to cut out the beam kick.
if you've not been before, be VERY careful, Sportstractor on here came out with me 2 weeks ago, and on a wet lap he introduced his S3 to the German armco after his evil haldex upset the car on the exit of a bend and sent us into a tank slapper!
otherwise, enjoy it! and try not to chase lap times