Don't assume it's a fuse issue Gary. Even it it has blown, why?
Exactly, if it is just a fuse great, and easy to rectify but the "normal" issue on a trad of this vintage is the stop light switch. This is operated by hydraulic pressure in the brake line, and is usually found on top of the chassis rail on the left side of the engine compartment. Not the most difficult of diy tasks but access can be awkward unless you have a ramp/lift.
The biggest problem is getting the old switch out without damaging the brake lines into the union.
