It turned out that the mirror switch worked fine, but it was so nicely made that I thought I’d post some pictures anyway. Step 1 remove the switch by prising it out of the driver’s door. The clips are in the middle of the top and bottom of the switch.
Step 2 Holding the switch with the connectors upwards, prise the back off by easing open the clips on each side.
Step 3 clean the gold contacts on the circuit board
Step 4 clip the switch back together (keep the switch facing down and place the circuit board on top, then click it back into place
Step 5 plug it back in :-)