Gavin - the cold bothers me, I just cannot function if I am cold and the winter is good build time. But I have a plan....
2 or 3 small oil filled radiators, one in the main part of the garage which in the coldest periods will be left on all the time to keep the worse of the chill off and one or two (I will see how it goes) in the workbench area. I will also have a fan heater on standby to give the space a blast of hot air to get temperature up to a comfiortable level when needed.
I also, before next winter, will get something to cut down on the draft coming through the garage door. I dont know what yet so if anyone has any ideas? The garage will rarely if ever be used as a gaage incidentally but I don't think I can get a more permanent solution like a stud wall inside the garage door past the missus.
I am planning a moveable partition as well to sit between the workspace and the main garage that has thermal properties, as that may help keep more of the heat in the area where I will want it.