Installing 113 important updates to Win 8.1, and this is after installing the previous 83 important ones.... I'm still slightly puzzled why they have offered me Win 10 on the laptop, but not this desktop PC. they each have their own kosher versions of Win 8.1.
Aha, I've had a thought. The bastards are possibly not offering it to owners of OEM versions of Win 8.1. How kind of them... but surely the laptop, which was bought ready installed, must also have an OEM version, I must check its number.