Tiling disaster! What can we do?

[Naicecuppatea]

We recently spent a lot of money on re-doing our kitchen and two bathrooms. The same builder did all of it. Few months down the line and we have problems with the grout cracking between all of the tiles in certain areas, tiles popping off the bathroom wall, and the floor tiles in the kitchen, which is a large area, becoming unadhered (they make a noise when stepping in certain areas and some sound hollow). The builder has been back in to regrout areas in the bathroom but there are still the same problems.

He has since been in and tutted, but I honestly think he doesn't have a clue what the problem is and worse, we don't trust him to sort it out properly. The kitchen floor tiles are over underfloor heating which may make fixing it more complicated. I can't see any other solution than him taking all the tiles up and re-doing the entire area, which may mean some kitchen units needing to be moved as well.

We are gutted, the tiles were not cheap (Mandarin Stone) and we love them and we just want the job to be over and done properly, after one year almost.

Any similar stories, possible solutions, would be extremely appreciated.