Most of the rotary operators get involved in Silverstone, but most operate from temporary sites in fields surrounding the Silverstone area. I know only one operates from Kidlington Airport and they are one of the largest operations on the day. A number of operators also do special shuttles from private sites and Battersea for clients who will pay for it! But as PACO says, just call up some operators and ask them, or check out their websites.
Just about every helicopter type gets involved. The larger S61's and Super Puma's from the north sea and Scilly's are hired out by the operators and come down for the weekend and there are also R44's buzzing in, along with everything in between depending on what is available.
I believe that Silverstone set up their own operating team for the weekend, but they are fantastic both in the build up and over the weekend.
The operations to other events, Chelt GC, Ascot etc are nowhere near as big due to less demand, although they do operate. Cheltenham GC is operated by a company called Helicopter & Aviation Services, or something similar, who run an events team.
J