It depends on your principles,… and there are plenty other agencies around for him
On other hand IF he wants to stay there for whatever reason, it is only 200 quid And rather than be 200 quid down, there are more ways than one of skinning a cat when ‘working within’ if you are astute enough.
But by the o/p’s attitude and replies to his boss after his f/up I aint sure that he is tbh.