I've had serious problems with a tiler I found on mybuilder and what I've been left with is a bathroom floor which has a heck of a lot of movement and the grout has all cracked. It's a high water area so obviously I'm extremely worried and it all has to be ripped up. It's a tiny space - only 18 x 33cm square tiles - but the tiler said he would come back twice and then disappeared. He also tiled the WC, and there is movement there too but the grout hasn't cracked (I'm less worried about the movement as there is no shower or bath in this room, but maybe I should be worried?). The problems, I think, are these: 1) He didn't secure a loose floorboard. He then blamed me, saying 'I expect a customer to know their own floor'!!! God forbid he ever works with any of our elderly in this country, or anybody who isn't a tiling expert in fact! 2) He used ditra on top of floorboard and that's it. Should the floorboards have been removed entirely and replaced with thick ply? As it is, there is a ledge and floorboard and ply would leave a ledge of about an inch! Would Hardie backer work on top of the existing floorboards? Or not thick and secure enough? Is the safest way to replace the floorboards with 25mm marine ply (and with ditra as a decoupler on top? Or no ditra?) I've heard some people say that ply, even marine ply, is inappropriate in a bathroom. What then is appropriate?!