Well, firstly, VDO Seimens ( in Birmingham I think) are damn hard to get hold of. They never answered any of my mails.
Then their automated phone system is pretty poor.
If anyone does try to contact them (on this number >> 0121 326 1234) don't push any buttons on your phone. Just wait to be put through then ask for technical.
Anyway, VDO say that the unit should work with all 'Tuner List' radios but has problems with some of the newer ('05 onwards) 'Update List' units. The chap I spoke to said that these renault units have had some kind of external mod making them incompatible with the standard CHM 604.
Therefore, he comfirmed that if this is the case, you will need the new CHM 604 / 62 which is the same unit but with the incompatability fixed. I asked if there were any mods that could be done with the standard CHM 604 unit to make it work but he said no (probably didn't want me to kill myself?)
So, You need to check with VDO CHM604 suppliers and specifically ask for the '62 variation.
I'm glad I've got to the bottom of this although I'm irritated that both Renault (and VDO initially) said the standard CHM 604 would work. (and now I'm currently £250 out of pocket for 2 units)
I sincerely hope this thread has or will prove useful to someone else. Hopefully it will stop others having to trawl the internet for fragments of clues like I did. (and put up with reading pages and pages of badly translated french. (Zoot Alores!!)
As you were. Over and out