Thanks for the re-assurance that this "grey" software market is actually pretty much legitimate.
On reflection I suppose it's a tacit way of sweeping up customers who, in years gone by, would pay upgrade prices rather than full package prices. Which always seemed a fair way to go about things when folk don't really need whatever the upgrade brings. Like me. All I want is to run the same, relatively simple things, on an a new computer. For me any Office upgrade benefits fell off around Word 5 era.
Agree with David that it's not worth hunting to save a pound or two. My usual rule for everything from insurance onwards is that hunting, and switching, needs to save £50 or more to be worth the effort.
Libre Office is interesting. I did take a look at the last computer upgrade to my workshop computer over 10 years ago but something fairly minor didn't go right so decided I didn't want to risk compatibility issues between the workshop computer and the laptop, house, computer. Could well have been a fat finger issue but sometimes life is too short.
I use the workshop computer, one of the old Mac Pros with a big screen and 4 drives inside, for most serious work anyway as it's much easier on the big screen. That one is locked to High Sierra so I can run my CAD program. VectorWorks, ex-Mini-CAD, which not only hasn't had the mechanical drawing package updated for years but also has gone to subscription only at £1,000 a year. Which isn't happening. Lord knows how I'll cope when that one dies with maybe 1,000 drawings on file!. Parallels desktop maybe.
Being paranoid I like the security of two synced computers on independent back up schedules for all the important stuff.
Thanks for the comments.
Clive