Mat is a really lovely guy, very kind and helpful. The room is in a basement which isn't entirely clear from the photos - which are slightly misleading in that there is no natural light in the room. It's a little damp because of the lack of ventilation. I guess if you had the whole apartment it'd be much more spacious and light on the top floor, but that is where the host lives I think! So half the photos aren't part of the rentable space.
However, if you're just wanting a place to sleep it's great. Very quiet and secluded and really close to the canal with some great restaurants and cafes on the waterfront. We enjoyed our time in Paris very much :)