I asked on this list a few years about negative scanning. The topic's come up again at http://saveaussiemusic.org/ , so I wrote this up:
http://wiki.saveaussiemusic.org/wiki/Negative_scanning (feel free to add, correct, etc - here is fine) - precis: flatbeds are unusable, Ion's is as bad as scanning a small print, professional ones are the only archival quality option.
I am now told that high-quality negative scanners are not being made any more, and the remaining ones are becoming precious commodities ...
And I'm still after anyone in London with a high-quality negative scanner to hand!
- d.