Alright! My girlfriends just phoned me to say that the stereo isn't working. When she got in the car it was switched off for some reason, and when she switched it on there was no volume from radio or cd. Also, she says she can't skip tracks using the head unit, and so has to use the steering wheel controls.

Any ideas what might be wrong here? Seems like a total mystery to me. Also, I wonder where this sits with the famous 3rd year dealer warranty.

Stereo warranty is with Blaupunkt not Fiat or the garage I'm afraid, wont even be considered in 3rd year.
My CD player in my GP wouldnt work yeterday but today it does!
Selecting CD gave me the message "no media found" and the radio came back on the channel I had on prior to selecting the CD, CD wouldnt eject... wouldnt play... this morning its got out of its little strop and playing nice again now...

Yeah, as ffoxy says, try leaving it over night. Or try unhook the battery for 5mins, it will cause the CAN network to reset all systems