Starter motor swapped for the one in the scrapper; started first time so result. Even better, I had a knackered starter in the shed and feom 2 dead starters managed to make 1 good one and put that back on the scrapper which now also starts and drives.
On a slightly less positive note I found where my coolant went - on the transmission tunnel carpet. So, either heater o-rings are shot (I've never done them) or the heater matrix is shot. Unfortunately, I have other jobs that have to be done before dark so it will have to wait for another weekend.