Thought that would get your attention !!
OK, I have managed to source a device that may solve some of the problems here.
This little box of tricks plugs in line with your head unit speaker outputs by means of an ISO style "T-Connector" and has a 3.5mm stereo audio input that can be used with your iPod/iPhone/MP3 device via the headphone socket. There is a volume control that needs to be located somewhere, (on a fly lead) and thats about it.
When the MP3 player is switched on, this box will auto detect the sound from your device, mute the sound from the head unit and play directly through the speakers using its own built in amplifier.
This means that whatever your standard setup (except those of you running BOSE, sorry guys) you can simply plug this in line and listen to your audio whilst retaining all the originality and features of the original head unit.
All track controls, etc, would be done on the device itself, and there is no integration with steering controls or display - this is purely a basic playback device to give you some sounds.
I`m haggling over the prices at the moment with the manufacturers, but am trying to get the RRP £149.99 price down to around the £99.99 mark - but that really depends on how many of you would be interested and what sort of quantity I have to import.
What are your thoughts?
:-?