As above, van rear door handle. I can turn the key to either position, but either way the handle just spins. Occasionally feels like it is about to catch and open but then seems to lose grip.

Any likely culprits before i take it off to inspect tomorrow?

take it apart clean all the brown rust/dried grease paste off it , make sure the sliding wedge, slides and that the keyway for it in the handle is there and not rotted away

its easy and obvious to a man of your talents,

Same problem on a recently purchased AZU.

Dismantle the handle and spindle.
The drive "pin " (ie. flat bit that pops up out of the spindle to engage outer handle when key is turned ) wears to a round edge that slips and lets handle spin.
You will see how it works on disassembly.
Cleaning the assembly and adding graphite only makes it more slippery.
Could be brazed and filed square but a lot of stuffing around.
Bite the bullet and buy a new spindle assembly ( 75mm long).. Same as 2cv sedan boot ?
Available from several suppliers in UK and Burton in Netherlands
Cost? around 10 Euros???
Cheers
Bob
( Australia)

Spot on Sean, thanks. Aldi ultrasonic cleaner to the rescue yet again.

Thanks for the reply Bob. Mine wasn't too worn but good to know that they are available.