I stayed at the Alexander's flat for four weeks. The house is located at the real center. In Paris, every house is close to metro but Alexandre's is 3 min walking distance yo chatelet de hall which is like center of station.
The room provided is very well equipped and big enough for two. It is very bright and clean.
Alexandra is a perfect host. She helped me cleaning my laundry, prepared a Sunday breakfast. She is a real walker. (Ask me to join them if I want to but I am kind of a lazy :) she is sensible and ready to help but if your are tired really thoughtful of being silence at home.
Definitely recommend.