After removing the door lock it was clear what was broken - one of the three black pins about which various levers rotate:
Attachment 68518
Got a price of $110 from a local breakers for a second hand one. When I went to pick it up, it was already broken - same pin (they'd just got it out of the vehicle for me, so they hadn't inspected it. I don't think they were trying to rip me off). I'd been wondering if it was a fault only with the drivers door, getting more shaken than the others as my 54kg wife slams it shut ... but no, the wrecker said it is all the doors. Which, as it is part of the locking mechanism, is logical. Which leaves us at Friday arvo with no door lock and needing the truck Saturday. And even if I got a second hand, or even new, part, it could break again.
On inspection, it looks like the black plastic pin was a shaft for the top of two levers lurking in the depths. 30-45 minutes with a small drill bit and a couple of screwdrivers saw three or four bits of plastic on the floor. The mechanism would now operate OK with a bit of jiggling with drivers or drill bits, but putting in a tiny pin wasn't going to do it. Fortunately our family motto (on the male side, anyway) is nunquam aliquid iace, so rifling through the odds and ends box brings to light a clevis pin, probably from Dad's Standard 8. As it is quite possible that not many members' Dads kept all the bits from their Standard 8, or conceivably never had one at all, it is 6.4mm diameter and 10.8mm total shaft length although slightly rounded at the end. I think 12mm would be the maximum, and 10.8 probably the minimum. The old pin hole was drilled out with a 6mm bit, giving the pin a good tight fit which a dab of Loctite would help.
Attachment 68519
Attachment 68520
Attachment 68521
Anyway, it works - almost. The door locks and unlocks with the key which actuates the CL for all the other doors, and the door opens on both internal and external handles. It unlocks with the central locking button, but is catching very slightly when using the CL to lock. The other doors all lock, just not the drivers door. As I won't pull it out again until next weekend (which probably means never), I'm posting this anyway.
Note, when re-installing the lock, thread the external handle rod through the blue plastic clip before putting in the bolts. And the guide for the window needs to be carefully positioned at the top or the window comes down the outside of the guide.
