We had to change time of arrival the same day which wasn't a problem for Caroline, who thankfully could welcome us a few hours later. She was lovely and easy to talk to despite the fact that we don't speak any french whatsoever, she gave us a tour around the house, showed us how the TV worked, gave us the wifi code and two sets of keys.
The place itself was amazing and we could not have wished for a better flat or location. The balcony was our favorite place, perfect for a sunny breakfast or a glass of wine in the evening. The place is located a 15 minute walk from Montmartre, just following the same street, where you get amazing views, a square of artists showing their work, cute cafes and restaurants. It was close to grocery stores and restaurants and the metro station was literally right outside the door. It took about 10-20 minutes to the centre of Paris depending on where you are going.
The flat is on the 5th floor with no elevator which wasn't a problem for us (we were just out of breath every time we reached the door) but it's not optimal if you've got a broken leg or anything similar.
10/10, we would definitely stay at Caroline's if we were to visit Paris again.