Hmmmm, thanks for your reply. I think you've confirmed my worst fears. I've stuffed it by formatting the original partition.
What gets me is that the redhat install didn't appear to give me a choice. I was trying to get it to clean install on the 1gb drive (separate drive, not just separate partition!) but it insisted that the primary had to be on the first drive it found.... grrrr.
Never mind. Start again, wiser and keener