wow!
thanks all for your help and detailed responses.
After starting this thread,
I went back and manually uploaded the 4.3.1 upgrade (NOT including he content folder) over the auto 4.3.1 update done early this morning.
Went to my admin login page and I was prompted to update the db. Did that.
And now I can log into my admin dashboard normally, and all my admin tools and functions are accessible again. Yay! We love it when that happens. ??
Not sure what happened, but it seems as if the auto upgrade got ‘hung’ at some point towards the end of operation.
I feel slightly tentative about saying this, but…
I think this problem, for me anyway, is now solved.