Hello, am new here, I’m a homeowner looking for advice on fixing what appears to be a botched bathroom refit approx 3 years ago (single contractor did the lot singlehandedly, walls & floor retiled and new suite) with multiple issues. Issues became apparent with crumbling grout, I didn’t investigate quickly enough (too busy), could see movement in tiles and naively assumed replacing with flexible grout would solve. On removing grout recently I discover 6mm ply subfloor ruined and a leak from VERY poorly fitted toilet waste (virtually no hangover between the connector and the wall soil pipe) secretly dribbling into gap in tiles with every flush. Sub floor wrecked, black mould where tile adhesive used to be etc. Ripped out that section of floor (roughly 1 x 1.5 m) , replaced floor boards, want to avoid redoing whole floor. Planning to use Hardiebacker and foam on affected area and get in a pro tiler to re-lay. 3 questions - I can see some movement in 1 of the remaining newly exposed floorboards, will this be a problem? It goes under the remaining ply so fixing it will require ripping more tiles up. And...do I need to rip up the whole lot and start again? I’ve discovered another cracked tile away from the leak damaged area which sounds hollow when tapped so I guess the 6mm ply is flexing. Finally, do I have any comeback with the contractor (assuming he isn’t in jail for crimes against plumbing)? Any advice gratefully received...