"Only way out"
Only just visited here, so maybe someone has already corrected this, but there is also an exit to the coast road (A259?) through a low bridge under the railway at the opposite (South-West) corner of the airfield.
The Radio Amateurs Emergency Network (who were asisting RAFA and the organisers, as they were 7 years ago when the Hurricane crashed on the South Downs just North of the airfield) were asked again by the police to help close exits.
The concern at that time, and probably again yesterday, was traffic flooding out would add to congestion and enable "punters" to add to the jams that would hamper the Blue Light Services reaching the scene - Fortunately the nearest fire department are very close to the A27 Bypass at the next Eastward junction.
(ExSim - born and raised in the area)