Thank you for your help Hein!
I was not aware of the "Combine data from several providers" grabber in the web interface menu.
It seems to working nicely:
Jan 27 09:19:40 xmltv: Grabbing "Combine data from several other grabbers" using command "/usr/bin/tv_grab_combiner"
Jan 27 10:29:34 xmltv: /usr/bin/tv_grab_combiner: Parsing completed. XML contained 409 channels, 135584 events, 10136 new events injected in EPG
Jan 27 10:29:34 xmltv: Grabbing "Combine data from several other grabbers" using command "/usr/bin/tv_grab_combiner"
Jan 27 11:38:44 xmltv: /usr/bin/tv_grab_combiner: Parsing completed. XML contained 409 channels, 135584 events, 9 new events injected in EPG
Kjetil