How come it is possible to get 35mm stills negative and slide scanners for less than a couple of hundred pounds, yet it is apparently very difficult to find something similar with a computer controlled transport stuck on top so I can do frame by frame film reel transfers? Realistically, how hard would that be?

One of those machines with adapters for 8mm, 16mm, 35mm would be very handy.

Edit, incidentally, there is quite a good example of a home made hardware and software hack to get this functionality described here, with an example video (although the transfer looks a bit cool, or warm... whatever the right term for 'too blue' is in film).