Door Latch Dis-Assembly?

[Renaud]

Proof again that sleeping on it is always good!

[Chris KC]

Mais oui, "fools rush in..."
At the very least one should always make tea before getting the angle grinder out.

[Renaud]

Yes will have a drink here and scratch head... (maybe not tea though...)

[Duncan Grimmond]

I'd suggest that judicious use of a sharp, narrow (1/4"?) chisel with a small hammer could undo the peened square tube sufficiently to allow separation. Perhaps a spare piece of square bar in the peened hole would help to control the chisel's action. I have done this on (non-car) locks in the past with some success.
Depending on how much metal remains on the very worn-looking face I'd be tempted to braze or silver-solder a square (or even a stirrup shape) of steel sheet over it and file down to the original section. Take great care to avoid overheating that paper-thin part.

[Chris KC]

Thanks Duncan. Yes I agree - softly softly catchee monkey...
(Though why anyone would want to catch a monkey defeats me)

I have this evening found a couple of very helpful photos on the Nippy site which clarify things somewhat, thanks to whoever took those - though still a few little mysteries left to resolve.