Thanks for the advice everyone. Unfortunately I haven't had a chance to discuss the diet change with the vet yet. At this stage it looks like he might be at the vets for a couple more days, depending on his next blood tests. Just from a quick discussion with one of the nurses today, they suggested the chicken mince may be ok, definetly no carcases and I think they might want to put him on the Hills ID prescription diet dry food (glad I didn't buy another 15kg bag of Eagle Pack just yet!). From the advice everyone has given it sounds like his diet willl probably come down to just how sensitive he is.
He gets feed human grade chicken mince which usually looks pretty lean, but I'll talk to the vet about the roo mince. My only concern with the roo mince is he stools can be a bit loose if he gets too much. So perhaps a mix of roo and chicken mince?
I've sworn of greenies since I've been educated about them.