OK, so I've been buying more retro computing from eBay again.  This is the latest:

I remember that one of my school friends had one of these, it's only taken me a couple of decades to catch up.  So I've set about writing my own transfer software to move data between the Z88 and the PC.  So far I have a BBC Basic program that runs on the Z88 and a C# .Net application that runs on the PC.  Binary files can be transferred, so I can back up my files (including program listings) off the Z88.  Maybe I'll show you the cable I made, it's a serious DIY job.