The following two pictures show the left side of the ashtray.
The front of the ashtray mechanism is to the left on the pictures, rear to the right.
Note the silver pin in the centre of the image. This, it turns out was the problem with the ashtray not staying closed. it doesn’t act as a hinge or anything, instead it semi guides the locking mechanism. The pin on my ashtray was present and in position but had poped out slightly meaning whilst all the parts moved correctly, the ‘L shaped’ part behind the hinge (that the pin sits in) wasnt working correctly.
We joked about this being the ‘£150 pin’. Had we lost it, the only way to fix the issue would have been a new ashtray mechanism at circa £150!
I dropped the pin whilst trying to figure out what it did and trying to refit it. Fortunately I found the pin in between seat and door on the carpet (which given its dimunitive size is remarkably lucky – its circa 2mm diameter and about 10mm long at most).