Picked up a 500gb Seagate drive for £15 at CEX. Got the case open to find that the G5 has 2GB RAM and no hard disk, as expected, unfortunately the drive cradle is missing. Fortunately some meccano and a pair of pliers sufficed to knock something up - eventually I'll look at getting the real thing if I can. I'm now installing OSX 10.4, the last PPC version I have, and hope to have it up and running properly in the next few hours. The only problem is that the original drive must have had the drive light indicator socket at the other end from the other cables, it won't stretch to fit on this drive
Not sure where it will end up - I think someone in my family may like it.