I guess that confirms it for me then. I think I'll let my dad run out his Vista experience until next year on his laptop as well. We were considering bumping him up to Windows 7 and then 10. He can always get a cheap new laptop with Windows 10 next year since he only uses a browser and the occasional Word document anyway.
There's a tool by a well known security expert that makes it easy to change/remove a registry key that will prevent Windows 10 from downloading/installing:
https://www.grc.com/never10.htm Download button half way down the page on the right. Security expert. Definitely not a usability expert.
Also: sound warning when using the tool. Turn down your volume.
Turns out the girlfriend has been paying more attention than me. I already had 6,3GB worth of Windows 10 files on my laptop ready to be installed! Her laptop was clean. Damn it.
Removed that shit and disabled it with Never10 with two clicks.