I Hope it's OK to mention the magazine ( nothing to do with me ) but the mag' Flypast ' has covered the story of filming ' Battle of Britain ' quite extensively over recent issues.
Hamish Mahaddie initially reckoned he could source all necessary aircraft in the UK, but this proved optimistic.
The Spanish Air Force were extremely helpful with their ( Merlin powered ) HE111's, and a lot of the filming was done over Spain.
Incidentaly I recently met a chap who was involved in the filming, and operated a replica Hurricane, fitted with Jaguar engine for taxi-only use.
He reckons he got quite a long flight at an altitude of 8' out of it !
That 'aircraft', which looks very authentic, is now on display at Tangmere.