is your horn operated from the end of the stalk or the centre of the steering wheel ?

I've got my horns, operated on the end of the stalk, as below:



this is nothing like standard sierra horn wiring, but is simple and it works

and the windscreen washer :



again, this is not standard - remember I mentioned above about stalks with a seperate earth tag (1/4" push-on terminal) - but this seems simpler to me and easier to fault trace if necessary