Well I've done the cleaning thing, and I've done the unplug it for 30 minutes thing, all to no avail. I guess the drive unit must be shot, despite the power light being on and I can hear it reving up. So a replacement it must be it seems.

There are a few floating around eBay. Was thinking I'd upgrade to a Mark-IV unit while I'm at it. Presume it'll work ey ?

I'd like to be reasonably sure that if I buy a replacement unit that it'll actually work because they're not cheap. And the sellers tend to highlight on their ad's that there's no refund available on the items.