Re: It aint just this upgrade
"Used to switch to the US layout on my GB machine at random until i realised you need to change both locale and input settings. Buggy pos"
Hmm... I'd say more than half of the Windows 10 computers I've looked at have had a similar issue - in this case, computers in the UK which, after Windows 10 was forced on them, had the locale set incorrectly to US, which was affecting things like the keyboard layout. There's one user I can think of in particular, though, who didn't come to me with that problem.
However, I've just joined two random dots in my head. He does seem to have another issue; whenever he uses Google Docs, his spreadsheets default to US currency, and I have to keep showing him how to change it. I now wonder if this is related. (And I wonder if he does have the keyboard layout problem and has never mentioned it).