For future reference, clicking noise is the GEM module which is behind the fuse box.
Fog feed comes in on the blue plug. There's a fuse for this module is in the main rack which is labelled in the owners' manual, and one of three more on the GEM unit itself.
This particular fault was with the bulb holders, which annoyingly was one of the last things I checked. But the owner attempting to bridge one light to the other side is what caused the fuse to go - I assume the GEM unit can't supply enough current to power both lights which is why the fuse is rated quite low.
Now also stocking GEM units as I've had a few out to swap in to this car which are now on my shelf :lol:
All part numbers start YS6T-14K150 with the other two letters identifying the version.