In the early days of UNR there was an applet called Desktop Switcher which let you jump between Desktop and Classic modes. This was broken in 9.10 Karmic Koala and you had to jump through several hoops to get Classic back.
I was expecting similar difficulties with 10.4 Lucid Lynx and messed around uninstalling the ubuntu-netbook package and its dependencies to get what I wanted. Having got it working I re-read the bug report and noticed the comment right at the top which said that 10.4
will come with the ability to choose a UNR or regular session at the login screen as opposed to doing the switch liveSure enough, in the Session menu at the bottom of the login screen, you can select Gnome, UNE or xterm. Doh!