This was a tricky little tiling job. The choice of tiles didn't leave much room for error and the small area didn't help either. If you've never tiled before you are probably not aware that walls are not straight, level and vertical, they do not meet at right angles and are rarely parallel to each other. Floors are not much better. The tiler has to work out how to deal with these discrepancies  (0.5 mm is a significant error) hence the drylaying.