D2 mirror help.

As the title says i am looking for some help with the wiring for a auto dip mirror with map reading lights. Part number is CTB100130 if it helps.
It will be going into a discovery 2. The mirror has a 3 pin connector plug on it with white, black and grey wires. Any help appreciated as so far i can not find anything to tell me what wire does what. Thanks in advance.

White is usually live
Black is permanent ground
Grey is switched ground (via doors).

Or at least it was on a Mondeo one - no reason to suppose this will be different - try it with a battery.

Thanks, will give it a go.