No one knew the answer, so I sussed it myself!!
Multiboot was the key - I edited the fstab on the bloody wrong partition!! hahahahaha
The one I needed to edit was hda4, I was editing hda2 hahahaha
I looked at the one on hda4 and it was blank!! I put a single line in to mount the partition and put it as ext3 and rw,rebooted, and viola, knoppix hdd install sorted itself out and rejigged the fstab for me to add all the other drives!!

I'll try and help out in future if anyone gets a problem like this!

Muchimus gracias

Mors