Thanks for all the replies on this, very informative and helpful. We are definitely limited in cash, but what its really saying is that its worth going to some trouble to get a device which runs a 'proper' OS. Alas, the little Revo boxes are selling out before the funding comes through, so I may end up putting together a litte Atom bases ITX. There is a great little case available from Linitx for 20+ which you can put the integrated Intel board into. It will end up being more expensive, but also smaller.
I can see also there is more to be said for the Sheevaplug than I had realized, and apparently from the guides on the net, it is not too hard to install standard stripped down Debian on it. Restarting after power outage is quite an important feature if the staff are just going to call up and say 'its not working', and not realize they have to check and see if its turned on....
Cheers
Peter