Drivers
• All drivers must be 18 or over.
• All drivers must be at least 5’2” tall.
• All drivers MUST have a full driving license and MUST be able to display both parts on the day of the event.
• All drivers must attend a briefing before going out on track.
• Helmets are compulsory.
• Drivers must have arms & legs covered at all times whilst driving, no overalls will be available for hire on the day.
• Seatbelts are compulsory.
• Drivers must sign an indemnity and fill in all relevant track paperwork before going out on track.
• No hand held cameras allowed in cars when on circuit.
Vehicle restrictions:
• Your car must be in-keeping with Japfest.
• Your vehicle must be in suitable condition for circuit driving and to MOT test standards.
• Cars are permitted to use slick tyres if the weather conditions are suitable. This does not apply to Novice or Intermediate session drivers.
• Tyres must meet the recommended pressure for high speed driving.
• Do NOT overfill petrol tanks.
• 3 wheel cars are not permitted on the circuit.
• All vehicles will be sound checked prior to taking to the circuit.
• All vehicles must comply to the strict noise limit of 100db(A).
• Measured at ½ metre from the exhaust outlet at 4500rpm.
• Merlin Motorsport, located at the Circuit, offer a range of bolt-on “Silencing Accessories”
• The Castle Combe Marshals reserve the right to refuse any car from being driven on the circuit for whatever reason – their decision is final.
Just wouldn't like anyone kicked off there track time for the above reasons
The complete info is here.
http://www.japfest.co.uk/2012/05/15/track-time-rules/
. I don't think overalls are required but ur arms and legs must be covered. E.G no shorts or short sleeved T shirt. Im not sure on the helmet front tbh. Probably over tinterweb. I have one from my go carting days so im ok there 
