Thanks for your reply. It looks quite similar to my wiring. The red and two brown wires on my photo to up to the windlass switches. There is no voltage registering on the red wire which is the common wire to both switches.
I think I'll try a 12 v feed separately to the switch and see if that activates the windlass. Then it will be a matter of tracking the feed back to where the supply voltage has stopped feeding!
If I find a fuse I'll post a photo in the photos library!