There is XPUIPC, an equivalent, which serves most purposes (it's not from Pete Dowson though - he emailed me once about it, saying he was more interested now in sitting back and enjoying his retirement than making new modules: I dread the day you say the same thing, Dave!). It certainly all worked fine up till last week. Now, the top pane is filled in but the lower pain (active COM) is blank. Both little red squares at the bottom are red. Also, as I say, could even be Windows 10...
It is possible that XPUIPC is not working in the new X-Plane 11.50, which is a big upgrade, replacing Open GL with Vulkan & Metal (my frame rates have consequently jumped from a best of 60 (which was in any case more than enough!) to 170fps+). And no stutters.. silky smooth at all times.
Anyway, that's neither here nor there really. I will have a look at logs and so forth, and I will contact Ben again at PFEtoXPlane - he's been very helpful too.
Many thanks.