Mathylde's place used Host&Fly to manage the apartment key handover, cleaning etc.
The sheets on the main bed weren't big enough to cover the mattress. We were one given 1 set of towels (a hand towel and a shower towel) for 5 people - 2 parents and 3 teenagers.
The flat is right next to Gare du Nord (we knew this from the map), but this means you can't open the windows at night as the train noises are right below the window. As we were there in the summer and it was extremely hot, this was a problem.
The flat is owned by smokers, so if you're a smoker, no problem, but if not, the flat does smell significantly of smoke. I forgot to check when I booked it, so it wasn't great, but that's not the owner's fault.
I would recommend only booking this place if it's not being managed by Host&Fly and you are in genuine direct contact with the owners (and you're a smoker!) and it's not going to be too hot.