Some interesting information:
I was in CC South yesterday and had a chat with Andy who is the guy responsible for cleaning all the cars at CC south. He said he uses pressure washer with no problem. He said if you have a chip you need to be careful not to come very close and at an angle. As for underneath the car, he said no problem and damage could be done. He said one important area to clean is a groove between the chassis and the side wall and you reach it by opening the engine cover. Warm water will help
By the way, picked up my first Caterham yesterday and drove her all the way up north to Glasgow. She performed very well. Torrential rain near the border, but no problem what so ever.... Very excited.... (She is an interim car until i get my R300 in March.... Road sport SV, 2003, 1.8 K Rover, 140 bhp, 5 speed, 16 alloy, leather seat)