there's a green and white wire I cut from the main loom for the mirrors. I'm guessing that's the one that links to the switch. From what I can see the mirrors get their power from the ignition, which doesn't seem right somehow. Should be a relay in there like the windows. the mirrors work off the same relay btw.
I shall be pulling my dash out (again) tomorrow morning and laying the loom tidy. Will report on the wiring when it's done

this should help

yellow/black to power through window relay
green/white to loom through switch
brown... do I really need to say?
