I would be fairly sure that in 69 controlled airspace in the sth of england was nowhere near as extensive as it is now for obvious reasons. I know for a fact that quite a bit was filmed out of hawkinge which is right on the coast anyway - loads of open FIR. Apparently the weather was quite poor which caused major problems. Believe Group Captain Hamish Mahaddie (WW2 bomber pilot/pathfinder) was responsible for getting all the airframes and pilots in the right place at the right time - quite a challenge I'm led to believe.