Thanks folks!
@Lange_666 - Thanks for the heads-up. Being a cautious soul, I always set any software I install to prevent auto-update, so I'm still on V62 on the headset. I thought that I'd checked a "no auto update" option on the PC app, but I'll check again and if not, I'll use the workaround you linked to
@Mk1_Trebuchet - Yes, I've been checking source dates, but with my lack of knowledge of the tech, it's difficult to know which technologies have been superseded/side-lined and which are still viable. Having now got it working, I can definitely see the addictive potential!
A quick update:
I've now got VR working reliably (i.e. I can fire-it up repeatedly, not just by luck or accident!) albeit with some stutters and freezing.
My next step is to revisit the most recent optimisation videos/postings and try the different performance improvement suggestions.
Playing with Link vs. Virtual Desktop is another step to try, because I can now revert to a working setup if it all turns to poop!
I have an unused WiFi-6 router from a recent ISP upgrade, so I'll set that up as an access point to improve wireless performance (my current WiFi hub is 4 brick walls away from the headset).
Thanks to all for the help. I'm still cr4p at flying in DCS, but at least crashing and/or ejecting is more impressive in VR!