To finish the story, got an auto spark to look at it in the end. Tracked the problem down to loose wiring coming off the positive side of the battery causing the battery to keep momentarily disconnecting. The guy thought this was causing alternator regs to blow.
Reconditioned alternator and much improved wiring later, she's hot to trot, running better and starting fine (with the battery connected overnight). So that's good then. :grinning:
Thanks for the advice on it folks.
