wouldn’t there have been a message box to the effect that Windows 10 was being downloaded?
As regards my particular scenario, I gather that's not the case.
The instructions I've got are (and I'm quoting):
1)Reserve your free, full copy of Windows 10 now
2)Upgrade when you receive a notification that Windows 10 has downloaded and is ready for you.
3)Enjoy Windows 10 for free!
This all suggests to me that if I were to "reserve" my copy of Windows 10, nothing noticeable would happen until the download had completed - whereupon I would receive some sort of notification that the download had terminated.
But, of course, I'm not sure about any of this ;-)
Just looking at my Windows Update settings, I've gone with the recommended "Install updates automatically", and I'm still on Windows 7.
(But please don't assume that I therefore have complete faith in Microsoft. It's more a case of laziness, ignorance and apathy.)
Another thing I read and is not mentioned here is the fact that the upgrade now is free, and next year it is not. This is to pressure everybody to upgrade