I've just upgraded the firmware to v1.80 and as a result I have formatted and am using a 32gb small format thumb drive. Whilst I'm never going to use even 1% of the available space it was the smallest capacity drive I had going spare.

If you are still on an early firmware version (I was on v1.04) I'd suggest you upgrade a.s.a.p. because it is also hard to find smaller usb thumb drives that are compatible with the early firmware. Also I don't think you can upgrade the firmware from the usb drive on early firmware versions, a smartmedia failure could be tricky to resolve as that is also getting scarce.

Thanks again to you all for your help with this problem.