Wonderful ! Had no idea they had this offer on - thanks again MrSoundman for bringing this to my attention. Sad as it may sound, I may not be able to afford it before the offer expires, so I shall still try to get the 10.5 AI upgrade if I can. I discovered earlier I have an AI4 license activated on the old XP machine and stored in a Soft e-licenser. I tried to register it against my Steinberg account but got a message saying it was already registered to another user. Also tried to drag it to my USB dongle but that failed with a message about my software being too old. Installed the latest eLCC for XP but that still didn’t work. Nothing is easy ! 
I’ve started a separate thread about the licensing issue. Now - which of those guitars am I going to sell so I can buy the full 10.5 upgrade?