Wow. I'm impressed with my own ineptitude.
I was installing gentoo linux on a box that previously had on it suse and ubuntu. Now - how many of you rate the chances of that setup (with ubuntu and suse being spread across three partitions, that were combined pre-installation) resulting in an ubuntu-desktop running off my newly installed gentoo kernel, with the rest of the gentoo system invisible?
I managed it, and I have no idea how - I'd love to retrace my steps and find out, but it's just not going to happen (I haven't got another 4 hours to waste).
If anyone can give me a clue as to how I could have possibly acheived this? - please leave a comment as I'm itching to know.