The Cabasse Auditorium head unit does work with a parrot car kit (or anything else that interrupts the iso connectors), but if you take out the headunit you may be confused to find NO iso connectors! The auditorium DOES have ISO connectors, but they are not at the back of the head unit - in fact they are in the boot!
Because you have the 6-cd changer in the head unit itself, it has been necessary to locate the electronics (amplifier and tuner etc) in a unit elsewhere in the car. On the Grand Scenic it is behind the right hand side cover in the boot area. To get to the unit, remove the luggage cover, remove the torx screw on the luggage cover plastic support and the other torx screw at the opposite end of this piece of plastic. The carpeted side panel can then be removed and behind it (just near the backside of the petrol filler cap - you will find the electronics unit for the cabasse.
Now - before you start - the cables for the microphone and the parrot control unit are NOT long enough to reach from the dash to the boot. You need to cut each cable and solder in lengths of appropriate (in the case of the mic, shielded) cable to extend them to the right length. Be very careful to heat-shrink wrap (or tape) your soldered connections before testing!
Once your cables are extended, it's just a case of following the parrot instructions - except you are putting your parrot control unit in the boot instead of in the dash.
You then need to root the (extended) cables through from the boot to the dash/headlining. I found the easiest place to run cables was under the footplates (tip - start removing these from the back of the car forwards, and be careful - they crack easily and are expensive!!!!)