So, the horn was suddenly going on intermittently

[Bob T]

I checked the relay in the engine bay to see if it had failed closed but nope. Checked the wiring to see if it had chafed and was tracking to earth inside the steering column but nope there also. The blaring would come and go.
I was sick of it and likely the neighbours were too.
So next I took apart the assembly and checked the resistance through the copper horn ring to the steel side of the front of the wheel.
That is a Bingo. The vaccuum fitted foam insulator has deterioated to such an extent that it created a circuit thru the foam and made the earth loop complete.

I made a cheapo fix, as parts or hard to come by out here and I'm a big fan of doing it myself.
Got some heavy duty heatshrink and fitted it over the foam and profile cut it then cut another heatshrink ring for the other side and then reload the wire clip back on.
Works mint as, happy with that