Stuart,
I just HAD to look up Fox Tor Mires since I had never heard of it, although I had spent some of my youth tramping through similar areas of north Dartmoor.
This site (
Battle of Britain London Monument - F/Lt. W O L Smith) says the collision occurred near Bovey Tracey, a long way from Fox Tor.
Good luck with your search. I have always thought that the Whirlwind was a great-looking aircraft. It's a shame it was let down by its engines. Imagine what a Whirlwind with Merlins would have been like!