Figured that having many users on a machine would create an unwieldy login screen I ran this command:
sudo gconftool-2 --direct --config-source xml:readwrite:/etc/gconf/gconf.xml.defaults --type bool --set /apps/gdm/simple-greeter/disable_user_list true

which changes the login to a manually entered user/pass setup.

I'm using remastersys to remaster an installed Ubuntu and create a custom iso to install to a new machine. Seems to work a treat.