I have reverted back from 10 to 7 for quite a few clients.
All of them took under minutes, some instances pastel had to be reinstalled.
Otherwise everything else, Outlook mail accounts etc remain un affected.
If you have automatic updates setup to install automatically.
Very good chance your PC will restart and do the update itself.
Tip:
Turn updates to manual.
Disable and hide windows update KB3035583 (Windows 10 Upgrade).
Then you good to go.
That is only the notification, not the upgrade file.
As with the OP having an auto install, I've seen it on 1 laptop.
revert back to 7(client has a few progs that don't work in 10)
next day he goes on net.
his data (prepaid fortunately) goes for a fast walk
do the usual to prevent 10
next day same problem
then searching the deep underbelly of the www, I found something.
It involves editing the registry. and syswow files....
there are 2 files the GWX you know and GWXtrigger
