Windows 10 Update 1903 renames User fiolder

Thanks.  Yes I started off with a Roll Back, then removed ZUNE etc. before successfully upgrading to 1903.

You are now in a situation without the upgrade, with MS saying that support for your version 1803 (?) is ending soon?

That sadly is the case. I intend to do more research on other possible causes of the failure, deal with them, then make a second attempt! I upgraded Windows 10  original laptop to 1903 without problem, so suspect these maybe Windows 7 legacy issues. 

But I wanted to flag up that some of the elaborate suggestions made above were possibly not the best approaches for the relative novice!

I do have the Zune software installed, however, I noticed my original User Profile folder had Dropbox files left it in.  This too could be part of the problem.

Easiest fix is to make a new Profile and transfer your info to the profile.  If the update was successful I see no point in going nuts to try and undo the update just to fix the user profile.

I too have rogue zune files in my original profile. 

Sadly, I ran the update thinking it probably had downloaded already and just needed to install. I'm on a slow connection so I ran it, updated and cleaned up the previous files as I always do to free up space. 

So now... I don't have the option to roll back. What's my best option in this case?

You could try to create a local user account with admin rights, sign on and search your original profile for zune, delete that file (I think it was a dll winzune something), and then sign on with your original profile and see if that clears it up. If it does then you can delete that local account.