Just an update. I took the car back to Oakmere and they diagnosed it was a PCM replacement that was faulty. This is what they changed last year. The repair was completed with no charge. I have to say Oakmere were very good and the car is now back and working correctly hopefully for a while this time.
That PCB seems to be an integral part of switch complete with lead and plug as shown here with matching rear fog switch.
![[Linked Image]](https://i.imgur.com/DDo7cur.jpg)
Although this pic is from a Roadster it seems if the positioning is similar it could explain why your rear fog switch was affected on initial issue. Given the huge price of replacement and if only the PCB is affected it seems a home spun solution wouldn't be that difficult. On close inspection the PCB carries the LED illumination and a resistor to give the dimmer illumination. Even a bodge salvaging the working parts of an old switch would likely be more rugged than OE.
