Thanks pelaird - I suspected that might be the case with Groupy. As it was my only regular use of tabs, I just assumed that Groupy would do the job, but clearly I've misunderstood.
I can open and manipulate tab groups in Chrome's own group function (but thanks for the guide) - however, my failed objective is to make them PERSIST over both Chrome window closure and overnight PC re-boot. As I choose to start each day with all these tabs on my screen, I really don't fancy re-creating the groups every day!
Unfortunately I can't make the tabs appear in any regular order (which would partly overcome the need for grouping) - the sequence seems to be random - every day is different (I tried numbering their titles in the Windows StartUp folder, to no effect. If you know what drives the order, I'd be grateful to hear!). I also have them all recorded within the Chrome 'start' setting, so I'm not sure which is active (I suspect it's the Chrome ones).
John