HI Dan, congratulations on opening up Denmark to black powder propulsion - that's no small achievement I imagine. For many years I was the head of R&D at Estes-Cox, and I can tell you that the concept of R/C controlled rocketry comes up often within the community, but it's not a common activity at all in my experience. It's mostly constrained to rocket powered boost-gliders, and there is a small community in that field. The safety concerns and possible liability issues keep most people from pursuing the rocketry direction I imagine. As for commercially available products - Estes did make two versions of rocket powered R/C gliders, first in kit form, and later as ARF models, and they were fun to operate. A lot of folks have made their own design rocket powered boost gliders.
We also experimented with aircraft launched rockets, and boat launched rockets. While those were all a lot of fun, the marketing of such products was never pursued. I can tell you that it's fun to launch missiles from your R/C aircraft though!
Good luck with expanding rocketry in Demnark. I imagine it will be a good market.
Scott