"Does anyone know who flew the aerobatic sequences in the film?"
According to the IMDB database "Bunny" Currant plays himself in the film as "Hunter Leader", though uncredited.
Bunny Currant - Wikipedia, the free encyclopedia
This thread identifies some of the others, and the location as Ibsley
Presumably one or more of these did the flying sequences?
Battle of Britain pilots in First of the Few - Key Publishing Ltd Aviation Forums