Folding mirror issue also experienced here (MY05 4.8is).

Here are a couple of tips that may save some time:
1) You can identify which mirror has the faulty switch by manually folding the mirrors in and out and listening for the microswtich. Comparing one side to the other should reveal which one doesn't 'click'.

2) I my case the the plastic pivot points were too worn down to reattach the metal spring. The microswitch itself is almost symmetric so I simply moved the spring to the opposite end of the microswtich and remounted the switch in reverse orientation. It's a bit fiddly getting the switch back in due to the wire routing, but can be done and works fine for me.