Last lot of British ceramics I layed were more like chalk than ceramic. Very absorbant and sucks moisture out of adhesive way to quick so added more water than normal to mix and back buttering was essential
You've done a multitude of things wrong I'm afraid,
No primer
Used Larson 'adhesive'
No burning or keying of both surfaces
'Adhesive' mixed to tight
Wrong bedding in of tile
Some people in the past have claimed that this game isn't a trade, but a lot can go wrong without learning it correctly ehh😵
I think you've got the answers you'll need to get this situation resolved, good luck with it 🙂
One other question if I may.
I was going to lay floor tiles.
Then once gone off cover them.
Then move on to putting my final row of cut tiles on the wall (to meet new floor tile).
Then I was going to grout the walls.
Then grout the floor as I leave the room.
Is this right? Ie walking on the floor tiles prior to grout?
Maybe it's a daft question, I don't know?