Hi
Success! I am now running Ubuntu 10.10 and it is fine with no power issues. It will boot off battery fine and I can also remove the power adapter while it is running. Brilliant.
I did a fresh install - no power issues. I ran update manager, all updates installed - no power issues.
It must have been an upgrade issue before (from 9.10 to 10.04 to 10.10). Glad I set up a separate partition to save all my files on, it has made this trial and error a lot easier.
Simon