Ok so this morning I have found the cable, thanks to flybobbie, pull a bit through and changed the pins over in the plug, all good.

this is where the problems start.. but this is expected its a Z4 after all. The new led light fitting is the wrong shape

the opening in the boot is not completely rectangular the corners opposite the cable end are tapered a bit and to get the new light to fit in the opening it will need to be cut down as per the picture. Obviously only the back of the light needs cutting not the front face
when the corners are cut off right back to the aluminium heat shield it will fit. a bit of a work up all in all but the new light is a lot brighter.