Did you get a cable with the CHM unit?
The actual CD changer unit has a round din plug coming from the back and the Renault HU had a socket for a blue ISO plug. The cable that comes with the CHM604 has one of these connectors on each end.
I've got my CHM 604 / 62 unit now and it doesw ork although it has some (as yet unresolved) issues with my MP3 discs.
If these issues are something to do with the hardware (as opposed to my disc) I'm going to get my money back (after all this!!)
Also, ADDACHANGER.COM were great for pre-sales but have been totally awful after I paid. BEWARE