I have a older G5 powermac that i can no longer use, as all our machines are now later spec.
Its a great fast machine, and is much more stable than our current ones.
This spec is off the top of my head, as the machine is not in front of me right now. But should give a close indication.
Dual core 2ghz POwerPc.
4 gig RAM (might even be 8Gig, need to check)
2 internal drives
Extra ESATA card (two ports)
Extra FW800 card (two extra ports)
Comes with fresh install of OSX 10.5.
Also fully loaded with CS4 suite, and FCP studio.
Basically was our video workstation for quite a while.
Old machines dont hold much value, but this one will run fast and sweet if you dont need networked serviced macs. Great standalone workhorse.
So, £250 ovno
Only Caveat is that i cant post so you'd need to be local to Brighton.