HuntandFish, once again you are referencing to the ground.
L2driver, I'm trying to keep an open mind either way here, but I think you conceded to the opposition here
Train scenario: As long as the helicopter model is kept inside the cabin -yes the model helicopter will behave exactly the same stationary or at speed as it is not exposed to the relative wind on the outside. Same as a fly in an airliner at Mach 0.82
Surely if we take the parcel of air inside the train to be a free stream air flowing over the earth, then this is exactly how we fly everyday.
I also feel you mised a point made by the AAIB:
(ii)The Commander, who was the handling pilot at the time, shortly after takeoff inadvertantly allowed the airspeed and then the height to decrease whilst turning away from a strong gusting wind
If the wind is gusting, and most wind is to some degree, then as we turn into/out of it, we will experience a change in airpeed, but no more than we would experience anyway in level flight. The only difference I can see is that we find it harder to judge/cope with due to the constantly changing relative direction.