We had a wonderful stay at Sebastiano's apartment. It is located very close to the steps of Sacre Coeur and has many restaurants nearby. We had no issues communicating with Sebastiano, and he let us drop off our bags early, as we got there before the check-in time and he was in the middle of cleaning up the place. He was very helpful and gave us tips on where we could eat/shop nearby. The apartment was very clean, kitchen had all the essentials we needed for our one week stay, bed was good, wi-fi was fast. Also Sebastiano has a great movie collection which we never got around to watching considering we spent most of our day out. The noise level was also pretty low, with the exception of some weekend nights when someone in the building got home late & made a loud noise going up the stairs ( probably with high heels !) . We used the metro stations of Chateau Rouge or Anvers depending on where we wanted to go & where we would eat on our way to the station. We shopped for some basic groceries at the shop on the corner, and also picked up some more stuff from the Carre Four nearby.
Just a word of caution for those with weak knees that Montmarte is on a hill, so any apartment you live here will involve a climb, so keep that in mind.
Overall we had a great stay and would definitely recommend it to anyone visiting Paris, and wanting to live in Montmarte.