(I hope I may answer my own question, since I'm not the only one sitting on that horrible Vodafone, with ever changing allocations of muxes, services and channels.)
Since tvheadend does't do blind scans, after changes made by Vodafone in Germany (NRW), broadcasts may be inaccessible.
Starting with a correct mux, things might get restored, but often enough not fully successfully.
Therefore my following write-up, based on an earlier set of exchanges, especially with DeltaMikeCharlie [(https://tvheadend.org/u/DeltaMikeCharlie].
Install w_scan (Linux)
Perform a blind scan with w_scan that results in an actual configuration file for a blind scan, e.g. with
w_scan -f c -c DE -x > de-wscan
-f c stands for cable, -c DE for Germany, -x for the format of the file, and de-wscan is the name of the file as generated. (One may change it, but with de- it'll show under "Germany" later.)
Copy this file de-wscan wird into the directory reserved for pre-allocations, that is in this case /usr/share/tvheadend/data/dvb-scan/dvb-c, and restart tvheadend in order to pick this new list up.
In tvheadend under "Predefined muxes" "Germany: de-wscan" needs to be selected. Subsequently, all muxes should be listed, and listed with "OK" as scan results. Under "Services" all services should subsequently appear.
In tvheadend "Channels" remain allocated to services, and therefore must be deleted.
Only after the deletion of the "Channels", the services may be mapped to channels, with "Map services".
Control proper configuration in "Electronic Program Guide". All channels offered must be visible, and show up with their native names.
I hope, this can help others as well!
