The smoke from the leads is just the massive current required by the starter to start an engine with old, cold and therefore extremely vicous oil burning off the crap or any insulating tape etc. New leads would make a difference I guess. My tipper ram takes an age to retract in this weather, which would give you an indication of the state of the oil in the engine. Actually at the tip, its embarassing. The later smaller starters fitted in later Transits aren't up to the job and haven't got the torque I reckon in the extreme cold weather. Also you might lose a bit of compression in the cold with an old engine until it warms up and add to that the diesel is colder and thicker and needs more energy to compress to ignition. I should have done a service before it got this cold (Oil change, Fuel filter etc.) but it will start if its left under a tree overnight so whos bothered.

Leave a blanket over it overnight.
My Mk5 was biodegradable and disintegrated with time.
Ford. Committed to the Environment
Finally entered the 21st Century and bought a MK7. Oh Dear.