with many thanks to torpa for the diagram i have, i will be doing the mod on the weekend.
ill redraw the diagram a little and post it, as well as pics of the wiring as im doing it, up on probly sunday.
if anyone is intending to do it, get about 10cm of the mirror loom from the switch plug back, this will enable you to cut the plugs of your existing EB mirror wiring and wire up the switch plug.
mod and pics this weekend, be patient