Really appreciate all the replies thanks! I just need a product which guarantees a perfectly stable, crack free floor 10 yrs from now. I have no problem guarantying the quality of my work, just want the same back up from the products I use. We had a problem about 8 yrs or so back with NMP. The tile and adhesive had completely de bonded, coming clean off the boards. This was a commercial kitchen with a central drain. The client prepped the floor himself, I'm convinced he used a cheap layer forming primer which caused the problem. However, it did knock my confidence in it. So I'm thinking now Marmox boards maybe or Hardie. Have to admit, I've not used Hardie much.