Thanks for the quick reply Chuck! We're not friendly in England... ie : we don't talk to strangers and ask to borrow their radios! But good idea - I will see if there are any people around to ask...
The radio is the factory installed one, I believe. It is the CDR-22 (?) made by Becker for Porsche. To be honest, it is time for a new one, but can you imagine spending that dough so for the guy to say "it doesn't work, and you need pay XXX for us to diagnose and rip up the wiring".... horrible thought!