Well Duuuuhhhhh for me! You've seen stupid people doing this stupid thing very stupidly before haven't you? You're absolutely right, I had installed the Premium version which isn't what my licence covers. Thanks for clearing that up for me, you're a star.
Now to address the 1001 other things that will have gone wrong with an OS upgrade, (including, I suspect, expensive hardware upgrades this time as everything I have which still does its job perfectly now seems to be unsupported in Win10).