Not the worse job I've seen......how do you know the walls are flat?
Just because it's new it doesn't meen it's going to be flat I've tiled many new builds with dodgy walls.
I've also tiled many walls like yours I always advice a nice mosaic boarder to separate the old and new tiles this eliminate's any issues with different batches of tiles size wise and shading..
Of course more care could of been taken.......but getting a surveyor in......really. ..lol
Just because it's new it doesn't meen it's going to be flat I've tiled many new builds with dodgy walls.
I've also tiled many walls like yours I always advice a nice mosaic boarder to separate the old and new tiles this eliminate's any issues with different batches of tiles size wise and shading..
Of course more care could of been taken.......but getting a surveyor in......really. ..lol