10 years ago when I was working at GCCC (gold coast car sound) we had one of the demo mini's on the shop floor and the car was basically made with hidden wiring, the car had central locking but the doors had no wiring running to them, I have been looking for the contacts that were run on the door so I can fit them to my car and I finally found them on Jaycar earlier today.
http://jaycar.com.au/productView.asp?ID=LE8779&keywords=door&form=KEYWORD
I recommend these to anyone that wants to put speakers or a 2 wire central locking kit in their car as they really do tidy it up, the only problem you have is that they only work when the door is closed.
I am pretty sure that you guys can work out how they install, if not then I can tell you how.