No withdrawal, you show your ignorance further. Icing needs water, basic physics. You can fly VMC in minus twenty if you want to, IMC = water usually. Water + cold = ice. So yes, they would have flown at height if the weather was better and yes you would plan that way, this gives you an option of using the map on a different day when it is sunny
THERE WAS AND STILL IS NO NEED TO DO A FLIGHT PLAN. In the UK we are not like a lot of europe, there is no requirement on a VFR transit. In 6 years service in Ireland I only ever did 2 Flight Plans and that was for airways trips which was mandatory. So I repeat, THERE WAS AND STILL IS NO NEED TO DO A FLIGHT PLAN.
When you say flight plan, do you mean copies of the maps? That is not what a flight plan is old chap. Now..... the maps removed because of a test/demo..... give me strength..... are you really this thick?? Man, I was there, so were others, it just is not true!!!! Even if there was a map that was removed, the duty auth would have been a bog standard Puma pilot and that information almost certainly would have come out. Unless of course he was threatened with deathzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz zzzzz