Chugalug,
Your: ".....
Having to keep airframes in a warm hangar before start up is still SOP and I have had my Hercules so cossetted at Thule before start-up and TO...."
There was an embarrassing incident at Teesside many moons ago. The Vickers Viscount which was to fly the first service of the five LHR shuttlles of the day was tucked up nice and warm in the hangar. The Flight and Cabin crews were ready to perform. The PAX were sipping their last coffees in the Departure Lounge. All the omens were propitious.
The Hangar doors were frozen solid shut ! 
How long did it take to thaw them out ? Don't know.
D.