He damaged the extractor fan when putting it up because he forced it when he couldn't get the clips to line up, the housing is chewed up and the bearing is out, so the whole thing vibrates. He also wired the earth into the switched live terminal for the boost (it's marked T so maybe he thought Terre? No clue).
He left about 1m slack on the flex running from the built-in cooker hood to the isolator, and fed that cable through the 150mm hole cut in the top box for the ducting instead of the hole drilled in the back corner for the cable. Not a massive deal, will take a few minutes to redo but I shouldn't have to.
He unilaterally decided to change a socket position from down the side of the fridge to in a wall cabinet. We explained to him well in advance that there would be a ~100mm gap that might be hard to work in, so maybe do that that socket on the first fix. We also then said we could pull the fridge cabinet out to give him space to work when he came back (we left it attached with only 2 screws because we were pretty sure it was going to need to come out). Apparently his solution was to move a socket meant for a vacuum cleaner into a cupboard at eye height.
And just in general, everything is wonky. Extractor fan, every isolator, almost every socket. Only by a little bit but it's just sloppy.