Thanks for all your replies.
I'm inclined, after a night's sleep, to go with the accident in Scotland as the date of the death of one of the victims is the same as my 1st cousins and his obit states "drowned while on training exercise in Scotland". The fact that the death, as IMBER has put, was registered in Scotland more or less confirms it.
Andy, the report that Graham found is interesting. It seems, rather than being a crash, one of the planes on the exercise overshot the target dropzone, the sun shone on the green light, and the men jumped. Sadly, they were over the Firth of Tay, one can only imagine that the weight of their kit would have given them little chance of survival in the water. The War Diary report would be interesting, but only if you have time, and certainly not at the expense of any other research you have planned.
katiespitfire, interesting that the reunion is at Hardwick Hall as Bess of Hardwick (fascinating woman, and well worth reading about) is a distant ancestor of my wife Lynn. We visited the Hall earlier this year - magnificent!
I think this one can be put to bed now. Thanks to everyone for your help and input. I'll mark it completed but if you have any other info you can post it on here as I'll keep checking back. Or you can send me a PM
Tony