Georg,
If he doesn't chime-in here, I would suggest you send a PM to Marcin Kaluza - he's a highly knowledgeable and active member of this forum and may have some useful suggestions. In particular, one approach that comes to mind is that you find out which service providers in the EU use the Canon DreamLabo press. From what I'm reading this would seem to be the key to higher quality than a number of the labs are currently achieving with the HP Indigo machines that most of them are using; whether they are using them to full advantage being another question, but the alternative technology seems well worth exploring.