Could anyone advise on suitable keyboards that will operate with various audio software via a USB connection (or Firewire?). Cheers

A simple search on the net gives

Roland/EDIROL ED PC-300
Yamaha
Evolution
Midiman Keystation 49 Keystation 61 Oxygen8

plenty of choice…

I may add that some here had trouble getting the oxygen fully working, make a little search here…

As far as I know, no firewire yet (but with Mlan coming in X, could be a yamaha option…)

i have Oxygen 8 and its works fine for me. Just have to make sure you have a dedicated USB port (won't work off the keyboard free port) or use a USB hub and then must make sure OMS, Freemidi or Logic etc. is setup correctly to work with it.

I use mine to play live parts in Reason and to play Absynth 1.2. Also, I like the Oxy8 cause it can also function as a midi interface allowing to connect any midi device and control it from either a sequencer on your computer or use the keyboard to play it. The only downside I found about it was the pitchbend wheel was not real accurate. It worked immediately when pulling it down but pushing it up... therw was about 10 degrees of rotation before it actually registered. No a great big deal but a little disappointing.