We were three people to stay at Charles' apartment for a couple of days for a work-related conference. Let me just start by saying the the apartment's location is unbeatable. It's around a 1-2 minute walk from the arc de triomphe (which also connects most major metro lines!). There are many nice food and grocery places nearby - and a delicious bakery!
Charles and his mother - who welcomed us personally at the apartment - were very helpful and easy to communicate with. The apartment "feels" like an authentic Parisian (some creaking floors and door handles), but that adds to the charm.
I can 100% recommend staying there.