I traced the culprit which caused the short on the Fog lamp circuit. Disappointingly its the expensive Savage switch design that caused the problem.
I couldn't work it out for a while; when the switch light wires were plugged in I had a short from live to ground. When the wires were removed and I tested across the terminals no short?
It turned out plugging in the spade connector pushed the switch terminal a tiny amount into the switch casing which in turn shorted it against the side of the switch lamp back to ground.
My solution was to bend the positive lamp terminal on the switch about 30º so it could not move into the switch - simple modification & solved the problem:
All working now - my fog lamp working again and indicated by the switch lamp:
Savage switches look nice, but the internal design has some room for improvement IMHO.
Update - More detail during a later aux panel adjustment here.
