mines just done the same,turned out it was the relay,the relay number is 24,but you will have relay 53 for the horn,pop that one in place of the relay 24 and see if they work
the contacts on my relay were fairly burned
i checked that i had a live feed on the red wire,and earth on the brown wire and a positive ign feed on the black/yellow wire,but there was no feed on the red /black wire when i hit the switch,so knew it was the relay,also the ilumination on the switches had gone too