There is were the problem lays, if they are coming back to refit work that they are adamant there nothing up with why they coming back at all or subsequently if what you have said about the lack of adhesive coverage on the tiles originally why are you having them back
the architect who's managed the project said I need to give them the chance to rectify the problem. I've got them to redo just the hallway first (about 8 tiles) and since I work from home and have cameras fitted everywhere I can monitor their work.
sadly, I'm not sure if I'm in a position to demand they hire a professional tiler to carry out the works