OK, I'm good now.
Seeing as I was idle today I had another go at installing.
I uninstalled and cleaned up. And tried again, with particular attention to instructions. I just had the same result as before.
Uninstalled and cleaned up again. I rolled back Windows to before the Creator Update. This time, after installation I got a black screen with sound.
At this moment my DVD arrived in the mail.
Uninstalled and cleaned up again! Still black screen with sound.
Found this fix -
http://www.subsim.com/radioroom/show...&postcount=969
This resolved the issue.
Maybe this would have worked with the steam install and/or without rolling back the Creators Update - I don't know. For the moment I have a working installation after many many hours of trying, so I'm leaving it alone. If it breaks in future I'll experiment more, now I know how to ultimately get it working.
I'm currently on 388.43 with nvidia. The same results were noted with 387.92.
I hope posting my experience helps someone.