Richard, my understanding is it is the PCB. Bear in mind it is an older version than yours. Graham has had a look but couldn't solve it due to the useless new circuit diagrams.
If you want a go let me know.
OK that explains the situation better thanks John and sospan. I did edit my post to say I was referring to the 2014 onwards version (as illustrated) which uses external BCU control for timing of heated windscreen and headlamp state to control fog lights. It seems I made a false assumption the OP had this type since his was a 2014 car
Apologies for confusion.
