Thanks for the information Dirk.
The shops look promising and I will definitely have a closer look at them.

Yesterday evening my Robby RP6 was delivered! I was positively surprised by the quality of the robot. It all looks and feels very solid and made to last. Thanks to the extensive manual it was quite easy to setup the basics. Within half an hour I had uploaded my first example program and could let the robot run through the living room, finding its own way by avoiding the furniture.
See my blog for some first pictures.