Bongo Fury

For some reason my horn isn't working. It past it's MOT back in June. I've never tried to use it before I discovered it didn't work. Is there a button or something that disarms it? I wondered if I may have pressed something rather than it being broke?

No, simple switch on the steering wheel which operates a relay to sound the horn. Two very common problems;
1 - The horns at the front of the vehicle have corroded and need cleaning they get all the wind rain etc coming in from the radiator ventilation.
2 - The wiring up the steering column itself via the Squib can fail.

See here for horn positions https://www.lushprojects.com/bongoparts ... mgno=.html