I have fitted the Parrot CK3100 car kit to my 1.6 HDI VTR+ hatch. My C4 has not got the rear parking sensors fitted so I am unsure what problems you would have, if any? I fitted the kit into my C4 using the ISO adapter lead (cost about £15.00 on the internet) made the installation simple, and also mutes the radio when using your phone. Fitted the kit without drilling 1 hole in the car, used double sided sticky pads on both the control box and the visual display unit, and clipped the microphone to the front A pillar using the clips supplied with the kit, works great. The instruction with the kit is quite easy to follow, and the forum on the Parrot site is quite helpful.