well.. yeah Land Rover... trusty old bugger.. can't help you with the drafty doors.. it's a Land Rover, that wants to breath...

being a petrol head my self, used to drive a ex-MoD LR101 3.5Lt V8 petrol Soft-top from 1975 for 15 years on SU-carps... never encountered starting problems like you described, not even in Scandinavian winter, unless the battery was flat... sound's like you are pushing a diesel... hopefully not a TDI...

one tip.. if you want to hit the snow covered roads before 11am, even witout waiting for the sun to come up...well do what the local HGV driver do... make a fire in a bucket and push it under the engine sump to pre heat the engine.. sound's like you got non-winter diesel in your tank, where the diesel starting to get stiff and sluggish under constant sub-zero conditions.. you may mix some small amount of petrol or clean petroleum (but not the nice smelling flavoured one) in to the tank too..

about the rear door... grease in the door lock went stiff regarding the low temperature, which is normal in winter... don't worry about that...

hope that helps..
take care on the icy roads...

ps...
can't help my self, but have to declare the following:
Petrol is good for driving vehicles, may else...
Diesel is good for heating houses, may for ships as well...
LPG is good for cooking only (but not outdoors in winter), may useful for nice blow-up cine explosions effects as well..

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The trouble is that he was talking in philosophy, but they were listening in gibberish.