I have just added this to the map of places to fly your drone at Drone Scene:
Land owner permission not required.
The is a country lane on the West side of the circuit, with a couple of lay-bys.
Castle Combe Circuit is a motor racing circuit in Wiltshire, England, approximately 20 miles (32 km) from Bristol. The circuit is based on the perimeter track of a former World War II airfield, and was opened for racing in 1950.
The originator declared that this location was not inside a Flight Restriction Zone at the time of being flown on 16/09/2021. It remains the responsibility of any pilot to check for any changes before flying at the same location.