Retro fit cruise control to 2003 Z4 auto. What has already been said is true. All the wiring should already be in the car. To check this, pull down the lever for steering adjustment and undo phillips screw underneath, then remove the shell. Look for a small black wiring connection attached to the loom (there is a larger white one there also, don't known what that is for!) Now here is the good bit, I bought a cruise control switch from spares 24/7. £30 including vat and postage. The little black connector goes into the switch and the switch pushes into a holder. The lower shell has the cut out line on it and the space for the switch was easily cut with a coping saw and file. When you refit the shell make sure that the spire nut for the phillips screw is in position.