[jimh]

Done.
Only time will tell if it's better, but it works ok at the moment.

This switch has the rectangular connector. My car is a 51 plate FL.

They aren't actually enclosed microswitches.

The black plastic parts at 11 & 1 O'clock in the picture each have 3 metal cam followers in them (you can see the top one in the 1 O'clock part - the shiney metal bit).
The middle plastic part that rotates has 3 layers of cam lobes which act on the followers.
There are 3 copper "tracks" around the outside which connect to the various wires at each end, and in the middle. The beige plastic parts with the blue paint on them hold the outer 2 sections of the tracks inboard against the centre section of the tracks.
As the cam rotates it pushes the various followers out which push the copper tracks up and break the circuit. You can just see the contact points at the top of the 11 O'clock black plastic piece.

The contact points are like old distributor points used to be, or the inside of old electric window switches etc. They have a tungsten (or whatever) bump on them.
I ran some fine wet&dry paper between the contact points and sprayed them with some RS contact cleaner/treatment oil I had laying around.

Unfortunately, what I intended to do but forgot, was to take a picture of the metal side of the switch with the part number on it.

I think this design is better than the "track sweeper" version, although still not ideal, although I guess it's lasted longer than the intended life of the vehicle.

I also run an '85 Ur quattro, and a 2000 A3 1.8Tq so my idea of vehicle life is quite different to Audi's. I find the trick is to not tolerate anything not working as it should, then I stay on top of it...