This evening Windows told me that there was one update to install and did I want to install it. I clicked on 'Install' and in 5 minutes it restarted my computer and then told me 'Update complete'.
So it seems that all is well after all. Thanks to all for your input. I will wait and see what happens next before deciding what route to take. I was just a trifle baffled as to why it was taking so long. 12 plus hours to install seemed to be a bit OTT!
CC