I would say it was Henlow.

I went on ATC camp there in July 1965, and as Pagen says, there were a lot of aircraft gathered in store awaiting the opening of the RAF Museum. Among them were Lincoln RF398, which was parked outside the hangars like the one in shot, and Canberra B.2 WJ573, which was out to grass further out on the airfield. The Canberra was in the pale ‘PRU blue’ and grey colour scheme, and may be the one in the film. Also parked outside was Lancaster PA474, though this doesn’t appear in the film.

Happy Days

DD