We did not get to meet, but Jonathan was easy to get in touch with. I was greeted into the apartment by a lovely lady who I believe lives in the building. She showed me the apartment, and gave me all necessary info.
Jonathan's place is perfect for a one or two-person trip to Paris. There are boulangeries, cafés, corner shops etc. within a 5mn radius. Nation is 2mn down the street. Excellent location, great value.
One silly thing that might seem obvious but is not necessarily: when you want to open the outside gate from inside the courtyard, push the button on the right hand wall. Thank me later! :)