I just got an answer form autoleads:
"The protocol differences between Ford and Sony mean that the two are
incompatible without an adaptor lead, which incorporates a programmed chip
to handle this difference."

There is a company called ICD which has this lead in their program, but I couldn't find the website so far...

Looks like I'm going to throw away the Ford Radio :-(
I didn't want it in the first place, but it came for "free" and they couldn't even take it out ....

Anti