Thanks to all for inspiring replies.
TBH I´m thinking more and more about getting a conventional telescopic antenna with a reasonable priced "analogue" radio plus a remote which does not need a visible line. That´s about 140 Euros, speakers are in place anyway. The costs are justified considering to get traditional FM may be for 8 years plus. And it seems that other analogue aerial solutions do not work as well.
Currently I have a class D amp (just for mp3 players) which is a mess as it disturbs the weak FM i-pod receive in addition.
Only issue is that I´m not amused regarding the wholes to be drilled into the bodywork.
