Another unfortunate story of cowboy traders. Both should of know 6mm is not nearly good enough, your "tiler" certainly should. I'd use the word "tiler" loosely though looking at his fixing method. Looks like he's dot and dabbing! On a kitchen floor?? Even if the ply was substantial enough, a heavy foot in the wrong place or a fumble whilst drying the dishes would of caused a few probems as well.
