MythTv is a complicated beast - there are at least 40 software packages that need to be installed.
Having done that, I have discovered that although there is a myth-setup program, you need to first find some obscure documentation that tells you to run a script to establish an initial SQL database. Now, I knew that an SQL database was used, so the cryptic console messages were not all that cryptic. Nevertheless, it took a bit of finding to locate the script, and without detailed instructions on how to invoke it, and with which options, I would have been all at sea.
That done, I was able to run the setup program, and input the tv channels according to my previous experimentation.
However I can't get a picture. I can still run kdetv and watch no problem, but for some reason Myth is not reading the tuner card correctly.
Moreover, since re-booting, I can't start the myth backend anymore - a permissions problem, I think.
There is part of me that thinks that this geek-ish project is deliberately hard to implement - a sort of geekiness test. If you can't do lots of tweaking and configuring of scripts and config files manually, don't bother applying!
No time for more now.