So the Windows 10 upgrade on my Sony Ultrabook worked fine. Rather too well. Some time back I had to disable the touch screen on this device because the hardware has failed somewhere and detects two finger presses all the time. Which made controlling the machine rather tricky.
Anyhoo, of course the Windows 10 upgrade turned the touch screen back on. Thanks for that.
However, I've discovered that if I press down lots of points on the screen it kind of overloads and stops recognising things, so I can use the keyboard and mouse. But it did make some interesting gymnastics as I kept as many fingers as I could on the screen while opening Device Manager and disabling the touch screen driver.
It works fine now. Kudos to Microsoft for a very smooth upgrade on both the ultrabook and my twisty tablet.