you need to pull the steering cowling off to have a look first
the horm switch plug is at the top (little black plug which is a bastard to get disconnected)
short the 2 bits out with a poke of wire to see if the horn actually works
if thats the case then you will find that its either the push switch for the norn (which means getting a new switch) or the rings inside the stering wheel (been there, done that, almost impossible tosolder back on properly again) which means anotehr steering wheel