Group Polic
Only surefire way I can stop Windows 10 from surprise rebooting on me is to set this group policy:
Computer Configuration > Administrative Templates > Windows Components > Windows Updates > Configure Automatic Updates
To:
2 - Notify for Download and Auto-Install
That emulates the old Windows 7 "Check for Updates but let me choose whether to download and install them" setting - You kick off applying the updates whenever you're ready, and as long as you reboot yourself after application (IE: Don't leave the system in the update applied, awaiting restart state), The PC can't do it of it's own accord.
As it's Group Policy, it's only officially supported in Pro and Enterprise, and it's a power user only setting, as you have to pro-actively grab updates (Ironically causing the very issue Microsoft was trying to solve)
Biting the hand that feeds IT
