Hi,
I think I can bring something to this thread, as I've built (as a hobby) almost 100 converters (adaptors) for various Citroen/Peugeot/Opel (replacing OEM radios) and several head unit brands, so far just for Czech 'market' within last 12 months.
Have a look at this (Czech) website:
http://pavel.lajsner.sweb.cz/swc/ it gives all possible combinations what (new) radios can be controlled from which steering wheels (cars). Most of these combinations are not commercially available, that's why I've designed this converter (and especially the software for it). It's been very detective reverse engineering work to determine what's the format of messages that needs to be sent to the head units.
Google can translate this page in English fairly well :
http://translate.google.com/translate?j ... l=cs&tl=en
! can say that:
* PU2294 is Clarion
* your Xantia should have yellow MiniISO connector with four wires connected to steering wheel
* there's no compatibilty between steering wheels and brand head units, not even new Clarions with you PU2294 Clarion (except one Alpine unit that can learn your steering wheel)
* PSA engineers were very 'creative' in designing various versions of the steering wheel controls (there are ~10 different (= not compatible) versions used in PSA cars from 90's), unlike Opel which has just 1(!) version.
* your Panasonic head unit is very likely to be supported. There should be single brown-black wire on the back of the head unit connected to nowhere.
* I can build one for you, if you want. It's ~25€
Pavel