UPDATE: I have just phoned Cadwell Park to enquire about camping the night before or after. They say it is quite alright and sometimes a few people often do it. Fee is £5 sterling per head and no pitch fee for the tent. There are also showers and water available at the circuit too...
Sounds like i shall be going up on the Monday and getting a nice pitch.
Might even pop up earlier and watch some of the racing, as there is a bike track day on the 21st aswell.
Anyone else likely to camp if you come along???