I decided to install emacs 24 to try to get the full features of CEDET, and grabbed the 24.1.50.1 snapshot.
It installed fine and initially I was able to compile, upload to the board and display a serial terminal, it worked well and looked like I was in business.
I now find that I can't get the EDE arduino features - upload and serial terminal, and for the life of me can't find out why!
I've tried un-installing and re-installing all the emacs stuff, including renaming the ~/.emacs file and ~/.emacs.d directory, to no effect. I'm now at a loss as to what to try next and would welcome suggestions.
Jim