I intend to turn my integral double garage into a workshop/games room.

My plan is to erect a plasterboard stud wall in front of the existing garage doors which are to be left in situ. Any suggestions as to how best to weatherproof the doors from the inside. I thought of packing the gaps as best I can before lining with plastic sheeting then using 3x2 to build a frame,pack with insulation and then plasterboard. Does this sound ok?

The outer walls are brick and there are blocks on the inside. Would it be good enough just to line with plasterboard or would there be a considerable benefit in using 3x2 and insulation again. I would like it to be as warm as possible inside when finished.

When completed I intend to heat with either a convector heater or possibly an oil filled electric radiator. Any suggestions on most efficient/cost effective?

Finally any suggestions for good insulation material. Thanks in advance!

the best way depends on the thickness of the exposed wall behind the door. How much distance do you have to work with between the internal edge of the door and the internal face of the finished walls?