The double squared box symbol means it's double insulated and does not get earthed. The now spare earth wire should be sleaved (the green and yellow in the picture will be fine), and terminated (ie a connector put on the end) so it can't touch a live terminal.
I'm glad you didn't pay him for a rewire!
As a qualified and registered electrician, I would question if the guy has Any relevant quals.
As Duty Holder, the Landlord is ultimately responsible for the property and all works carried out. I don't believe an inspector has to be registered but he has...