Do they come on usually with main beam? If so, and the the full beams are still working, it wont be a fuse found in the fuseboxes- there may be an inline fuse fitted in the spots wiring- just follow it back form the lights to find it. If there is one and its good, check the relay- again follow the wire from the spots to find it. Get someone to operate the switch/ main beams and listen for a clicking- if you cant hear anything swap it.
Good luck. I hate wiring..