Mountain Man, are you raising your toilet pans and basins ? I have visited several properties with double tiling and it is surprising how difficult this makes a getting on and of the toilet. i know the raised height is possibly only 25mm or so but it does make a difference and the wash basin is also affected. My bathrooms were created it the 1960's and probably similar to yours are cemented in not glued and impossible to remove. I have been experimenting with Haymes seamless fleck 2 pack epoxy coating. Non slip I have even extended the floor coating into some showers.