My dad worked on the The Battle of Britain, he was part of the team of R/C modellers who built and flew the 90 odd R/C planes they used in the film. A few things I can recall he said about the film:
The R/C Stukas were powered by 15cc engines and were faster than the 10cc powered Spits and Hurricanes. They had to throttle them way back so the fighters could keep up.
There is a sequence where two Stukas dive bombing the radar station have a mid air collision. This wasn't originally in the script. Dad and another pilot had an accidental mid air while making dive bombing runs on a camera safety cage. They thought they were going to get reamed for wrecking two aircraft and holding up the shoot but the director was delighted and had the script rewritten to incorporate the shot.
All the R/C planes were destroyed in the film. The special effects guys put balloons filled with petrol in the fuselage and ignited them by R/C. This tended to just make the wings blow off in one piece so they started sawing part way through structural parts to make the plane break up more realistically. They also attached dummy pilots to the tail of some planes and released them just before the explosion.
Dad spent ages building three R/C He 111s for the film. The shape of the Heinkel was difficult to get right, lots of double curvatures etc. Also the thing has loads of individual bomb bay doors all of which had to work. What really annoyed him was that the film company got short of money and he never got to fly them. Instead they filled the nose with concrete, suspended them from a helicopter and dropped them into the sea. The sequence where you see all the tail surface control cables snapping on a HE 111 as the crew bail out is to disguise the fact that the dropping cables snapped on one of the aircraft and can be seen trailing as it hits the sea.
Dad's the guy to the left of the Heinkel.
