It seems like an excessive amount of damage for seemingly hollow plasterboard walls, but then I don't know f there is an unusual amount of noggins inside.
He should have taken notice when you asked about keeping the lights where they were, thankfully I think they could be put back leaving very minor repairs to the ceiling.
I'm surprised he didn't try to fit the plasterboard squares back for you, it's a poor state to leave it if there's no one else on board to repair it. This kind of repair goes with the job if there's no other trade present to do it.
Egg box walls are hard to get cables through, though there are various methods, alternatives, dodges etc.
There's often a better way to negotiate coving than his attempt. We all make mistakes, but damaged coving to that extent makes a difficult repair that often can't be totally disguised.
Cables would have been better in conduit where the wall has been dug out, but not a requirement so I won't go there.
Most of the cables seem to be in cable zones, but some are slightly out of it.
I think this bloke may be a bit inexperienced or just a bodger.
However, if you agreed to do repairs to the wall, I don't see you've got much of a case to be honest.
Was he prepared to put the lights back where you want them? There is no rule about putting them in the centre or anything like that. He does talk some rubbish.