I laid the tiles 25 years ago and forget the details. I think the tiles were placed on a bed of semi-dry sand and cement mix. The grout was of a type used at the time on industrial floors, and still looks well. The floor has never been re-grouted.
I'm not sure about the frost resistant...
Having just removed an old conservatory, I had planned to just mortar up to the level of the tile surface all around the exposed edges in order to prevent moisture from working its way underneath.
However, I am not sure that is this the best solution.
Is there a better way to weatherproof...