Ok finally a difinitive answer to my question, although this relates to Bayern/Bavaria ONLY. The girlfriend did a lot of xhasing on this for me and eventually had to call Nurnburg where she got the boss of the denkmalschutz, so you can take the answer as gospel.
Its not illegal to detect, like anywhere else worldwide you just don't go detecting historic sites or bodendenkmäler (places on the ground which are also protected) Pretending NOT to know is NO excuse, you will be hammered by the law whatever excuse you try.
A map of historic places (Bayern only) can be found under Bayerisches Landesamt für Denkmalpflege on the left hand side you'll see a map, this map is of the historic and protected sites, you'll need java to view (its also in German) He also said that only 2% of Bavaria is protected. So hopefully this helps others who might want to come to Bayern and detect