Today (26/1) I upgraded my GOG game with the latest patch and now ALL my savegames will not load and are returning with error 222.

Not at all amusing as I have spent many hours slowly exploring Act 1.

Is there anything I can do to fix this?

there was no patch today but the Mac players got both hotfix 16 & 17 so i'm going to assume you have a Mac

yes the code changes made a mess of crosssave because Larian changed their backend server without testing but that error code translates to "can not be accessed at this time" which on a Windows system would be restart & check permissions... on Mac its almost always permissions set wrong

First backup your save file(s). Actually always back up your save(s) after every game session.

Revert to your previous version of the game, which was working.

Thank you for the help and advice. I should have stated that I am using a Win10 platform. I have tried a number of possible remedies, but nothing had worked so far.
I do back up save games, a lifetime in the IT business has engrained some useful practices!

The problem has been fixed by reverting to the previous patch level.

For clarity, the patch for my Windows game that seemed to have caused the issue was Patch5, Hotfix6. I reverted to Patch5, Hotfix5 and save games now load again.

Awesome!

A quick search on google for error 222 seems to deal with triggers saved within a save file. So some decision/trigger that is saved in the save file is conflicting with something patch5-hotfix6 changed. I would search more of what error 222 is.
Even if you figured out what that trigger/decision is, there is no going back and changing it.

In the meantime, I would stop patching your game and just enjoy until the end. BUT continue to download the offline patches/hotfixes as they release, because there is a chance you will run into a game stopping bug and will be forced to patch the game. Hopefully, a later patch would resolve any issue you had with patch5-hotfix6.

patch 6 will be out soon on PC and that needs a new game so be aware