Both have now stopped working on my 03 elegance estate.Both bulbs replaced ,so must be wiring/switch(es) .Any help for a electrical nube gratefully received .PS (Towbar electrics fitted before my ownership)

Surely somebody here can help me? Wiring diagram would be very useful.

I think this stems from water ingress at the front, which soaks and rots the wiring. None of my interior lights (apart from the passenger puddle light!) works when I open the doors, which I put down to the wiring being damaged.