I will add that I've upgraded all my machines now with no real problems. Expect for Windows 7 that is.
An upgrade 'worked' in the sense that it loaded Windows 10 but a whole load of applications then refused to run properly - CS6 was one I remember - blue screens, various startup errors, activity cursor then nothing and so on. Can't remember all the ones that failed but the point is that I then ran a revert to previous OS.
That went fine BUT I still had all the errors
Looking at the various system folders there were an awful lot of files dated far more recently than they should be - so I guess that the revert ends up with a hybrid OS that includes Windows 10 files? Restoring a proper backup I'd taken before starting got me back to normal again. I tried this twice but no better the second time.
Gave up and used a new disk to run a clean install and got everything working eventually.