"I see the hangar doors have been shut whilst the aircraft is outside, this is a new one"
That's not at all unusual. Whenever she's been out to the engine testing pad the doors have been shut, only being opened again five or ten minutes before she returns.
The only times I can remember the doors remaining open when she was not in the hangar are when she was immediately outside being fuelled or defulled.
I can't imagine it is easy heating the hangar, especially with winter fast approaching. It would make no sense to leave the doors wide open.
Flip