Solution found. Once again (as usual) the answer is simple once you know it!
The clue was in the differing file types and my problem was not comprehending the entire print process across the network.
Foo2 allows one to use an HP1000 printer within Linux by converting the postscript output to a Zenographics ZjStream which the printer understands.
In the /var/cups/spool directory, the file that was "still" in Postscript format printed, the other was already converted and so didn't get printed. My testing with my old Debian laptop showed a document that was delivered in Postscript format. Which made the penny drop.
Since Linux/Unix/*nix uses Postscript as it's default. So all *nix connections would of course work AND it showed that Windows wasn't delivering in Postscript, it was in fact delivering it already converted for the HP1000 in Zenographics ZjStream format!
When I had installed the network printer on Windows, I naturally went with the driver/configuration for the actual printer HP1000. This is where all the grief occurred - I switched it over to Postscript and voila - it works....
Sigh - hopefully my pain will help someone else overcome their challenges faster than I did over this one!
You can get the Adobe Generic Postscript Driver here...
Thanks Rick - your suggestion helped me track down the problem. All this time I was beating my head against Linux and it was Windows that was the problem (no surprises there!)