Well done John. I have the same kind of trouble and also no solution. Changed the battery 2 years ago because it was losing charge overnight. Had it tested but both battery and alternator were fine, isolated the battery overnight and next morning it started fine. Then got fed up disconnecting and changed the battery which has worked ok for 2 years. Now the same trouble again - is it the colder weather? This time however the car is also taking longer to fire up even when jump starting from another battery. Changed the heater plugs a few weeks ago but no different. Isolating the battery overnight again but this morning it turned about a dozen times without starting and then the battery died. Going to buy a new battery today - this one only had 1 year warranty. But still think something is draining the charge overnight. Maybe when the battery is new and strong the overnight drain has little effect and then as the battery gets older and weaker the drain has a greater effect? The longer cranking time is maybe a separate issue - maybe losing diesel supply when parked overnight? Hard to get anyone to sort these cold start problems because once it starts then its fine for the rest of the day so I can't show a mechanic whats happening. Just putting this on the forum hoping it may ring true with someone else.