On Nov 15, 12:20 pm, "Uncle Marvo"
Volvo's have the option, probably best left to the Swedes which can
automatically turn your car heater on at a given time so you can
return to it nice and warm

... so you can return to it with the battery nice and flat?

My BMW has this option but it's a seperate petrol driven engine...

I dare to say that I just use hot water from the tap and await the
usual replies about whether you should or shouldn't.