Horn Sounds on its own.

Yet another problem with one of my two daughters Mini`s,this time the 03 Cooper.

The horn hasn`t worked since the last mot,i was led to believe it was a steering wheel problem,now the horn decides to operate randomly on its own as she is driving,it also beeps once when she locks the car remotely.

i have disconnected the horns for now.

Any ideas?
Cheers
Steve