Following my previous (frustrated) comment, i did some more googling, and discovered yes, there are in fact two Library folders, just as you suggest above, and I was looking in the root of Mac HD, as i was unware that this was the case. I thought i was looking at the only Library folder.
I learned of the "show library folder" check box in the Finder> View> Show View Options window, and navigating through this Library folder, indeed the file structure you had suggested was in place. I copied all the .cui files as you instructed, and it is now working!
So thank you, a very frustrating day has ended happily for me, thankfully.
Although, humbly, with your help i have solved my trouble, i still find it extremly disappointing that a problem that people seem to have been having stretching back to the 2013 version, still requires that amount of intervention by the user. I worked in (PC based) IT support 12 years ago, so i have some understanding of system files, and it fooled me. Software of this quality (and indeed cost!) should install correctly itself, nothing else i have ever installed requires me to make hidden system files visible, then copy and paste specific system files to a deep rooted file location. Its pretty poor service by Autodesk in my opinion, especially i have wasted large parts of today installing, restarting, uninstalling, restarting, installing, googling... you get the idea!
I hope this gets fixed in the future.
