And after that 18 hours of upgrade, including apparently a full download of the OS despite the fact that I had the alternate CD-ROM, the upgrade halts with "The upgrade aborts now. Your system could be in an unusable state. A recovery will run now (dpkg --configure -a).".

Issues

1. The first upgrade run started to download everything, so I killed that
2. The second upgrade run, I selected the "don't check for newer packages" option, but it still went online and downloaded at 100 kbytes/sec. I killed that too.
3. The third run, I unchecked the update option and pulled out the ethernet, so it had to stay offline. This update flew along, but then halted as KDE and some edubuntu bits were missing. Roll back time.
4. The forth run I put the LAN card in and left it overnight. Except of course every so often it halts with a dialog, so the morning was spent hitting yes or no then going away for an hour.
5. It's this forth run that has failed with some edubuntu installed.

6. I'm not that happy. I don't want to waste another 24h playing around with slightly different options. The contingency plan is kill -9 the installer program and reboot; see what happens. If that fails, time to be more ruthless.