Thanks guys
I managed to get a bit further with install, as suggested swapped in a diff DVD drive/disk and image, install got all the way to the grub fix issue with the older Debian installers and failed for reasons I can't explain,
I managed to clone what was a hd with a broken Debian install from a diff g5 using gparted and it miraculously booted
Just need to figure out now how to set the fans to max speed to stop it overheating like the last g5
I might give the Ubuntu remixes a whirl when I get the chance
Which of the ppc64 distros would you say has the best package support? I wish all Linux package managers were p2p, it wouldn't be so hard finding old packages