I stayed for 5 nights with my mum and sister in Alexander's charming flat in Bastille.
Pros: It had all the amenities that were required for a pleasant stay. The flat also was warm in late December which was much appreciated. The sofa bed was indeed comfortable. Alexander had left several guide books, maps and information about Paris in the flat which was very useful. In terms of location, it is less than five minutes away from Ledru-Rollin metro station, which is a perfect transport link. It is also very close to a large supermarket. With a little bit further of a walk, you would end up in Bastille, which has lots of shops and restaurants ans a really nice market, which I would recommend.
Cons: The flat in on the fourth floor which means that it's not for the frail. The flat also does smell like smoke, if you have a problem with that.
Overall there was not much wrong with the flat and I would recommend staying at Alexander's flat where we had a great time.