I tried the upgrade about 8-9 times and each time it got as far as the Upgrading Windows stage which is in 3 parts. On the second of these 'installing features and drivers' it would always fail and always on precisely 40% of the upgrade stage and 23% of the 'drivers' part. (It took hours sometimes to get to that point). None of the proposed online solutions helped.
What the problem seems to have been was the M-Audio Delta 2496 soundcard which is now a legacy device and, as I've just found, has no driver support in W10. A couple of days ago I tried with this taken out and the upgrade went through. I put it back in and the card won't work but W10 working OK. So I need a new soundcard.
I also had the iLok Manager problem but found a good solution online (on the V I Control forum) which iirc simply involved going to Services and starting Pace there.