I take that back actually. I just assumed the mic wiring pins were going to the bluetooth module, but they may not be!!
From what I can see online the mic is wired straight to the quadlock on an RNS with voice control, whereas they go to the bluetooth module in other cases. I haven't had a chance to strip the radio out again for a look, but assuming this is the case in my car, is it just a case of removing the 2 pins from the quadlock and fitting them in the bluetooth plug? Are the pins the same size?