If u don't mind, I've got one more little question...!? There is a full height cupboard directly behind the toilet on the other side of the brick wall. I need to bring the hot and cold copper pipes through the wall and then through the false tiled wall to feed a sink that will be opposite the toilet. Should I plumb all this in before I tile or after? (Drilling the holes in the laid tiles) cheers.Thats great, so really, whatever the wall substraight turns out to be, acrylic primer bal apd will work fine? If that's the case then problem solved! And thanks very much for your help to all who commented 👍