@ Ann - the issue is Ann, that I never installed Silverfast Ai - I just used the Epson Scan until now. This means that, as I don't have the serial number and the software has never been installed on my machine, I'm scuppered if they won't provide me with a new disk or a key to download the latest version.
@ Peter (et al) I finally found that once I'd selected "transparency" and gone onto the "Crop" tab and selected crop size 6x6 and "multi-crop" MF, it's providing me with automatic (but customisable) marquees that allow me to scan negs how I want.
Thank Wodin for that, I thought I was going to have a complete sense of humour failure over the whole thing and go back to digital....
Just to prove I've managed to do it, here's a couple I prepared earlier. I've applied a slightly pink-ish mono preset to them in Lightroom 2. The watermark will have to go, so I'll have to buy the software....
Thanks to everyone who helped and contributed to me keeping what's left of my sanity. Great support network...