B
Blunt Tool
When he comes back tell him you have sought professional advice and that he should have checked to see if bath was level and walls were plumb before he started whole tiles from either. Ask if he has put any form of bonding agent on loose old patchy plaster walls before tile adhesive. Also has he even set out to see if there is a nice size cut at ceiling and floor or is it just a lottery to see if he is lucky! Tile grout lines should be nice and even, plumb and level and no tile edge sticking out past another. Adhesive should be applied to walls and tiles coated on the back to compensate for poor existing walls. Tell him to stop, and go and find a reputable tiler preferably one who can give you references of past work, be prepared to pay a little extra to get a professional job!