I got fed up waiting for the Windows 10 upgrade to start by itself.
Downloaded the ISO and used that instead.
I wanted to do an upgrade keeping all my apps and settings, no clean install for this PC as it would take an age to setup again.
Insurance
I used acronis to clone the boot drive to a spare HD just in case it all turned to brown runny stuff.
I extracted the files from the ISO to a folder on my d drive and started the setup from that.
Told it to keep my apps and settings and let it do it's thing.
All went smoothly but was taking a while so I fell asleep.
Woke up to find it finished and just a couple of prompts left to answer.
I chose custom not express and ran through turning things on/off and chose the apps, edge etc.
My accounts were still intact and I logged in as normal.
So far only thing I felt an immediate need to do was find iexplorer and drag it to the task bar.
Edge didn't have my favourites and I need those !!
Might do an export of the favourites some time.
I didn't at any time enter a key.
If it prompted for one when it was unattended I don't know, but the install finished without me entering one.
Shows as activated so no problem there.
All in all went very smoothly.