Spoke too soon - ashtray is now removed, using the following advice:
"The little lid that covers the ashtray when it's closed also works the catch that holds the drawer in. Pull the drawer open until it stops, then push it about a half inch back in. Push the lid down to release the catch, then pull the drawer out. Mine sticks a little bit, and it's pain to get back in (you have to get the rails lined up), but it does come out."

Ok, so I think the switch is faulty - I've tried testing continuity across the various contacts with the switch in various positions - with all the car electrics turned off - it seems all positions are open circuit. Assume this is a valid test, and that I don't need to test with electrics on (as it's a mechanical switch not a logic one)?

Next question - how to remove the switch - I can see a single small screw that looks to be holding the switch assembly to the panel. Do I just unscrew this?