Horn Problem

[Mr Hardware]

So i was asleep in bed on saturday night, having a most wonderful sleep, and i wake up, i said whats that noise, and wifey says 'is that your car'?

And sure enough it was, the horn had stuck on. Very, very unimpressed (as im sure the neighbours were too) at it all. So i hit the horn button on the steering wheel and it stopped. This isnt the first time that this has happened, last time the air was very, very humid it did it too, but that was about a year ago. So i pulled out the relay anyway.

So i'm wondering, i guess its only two things it'd be, either the horn button in the steering wheel (do not want) or the actual horn itself behind the grille.

Opinions? is this a known problem? Is there a known fix?