Have a look at the British Motorsport Marshals Club website http://www.marshals.co.uk/. From their FAQ:
What duties do BMMC Marshals cover?
According to experience, the jobs include: Post Chief, incident officer, experienced marshal (flag & incident), track marshal,spectator marshal, race administration, paddock marshal, pit marshal, startline marshal, telephonist, rescue unit crew, rally stage marshal, rally timekeeper, passage control marshal, sector marshal etc. etc. The list is almost endless. BMMC members include doctors, scrutineers, timekeepers, ambulance drivers, firemen and commentators. In fact BMMC members can and do perform every official job function at all levels of the sport.
The club was responsible for establishing the Emergency Services teams at Silverstone, Donington and Cadwell Park and provides the vast majority of their personnel.