We really enjoyed our stay with Carlos and Reyes.
They informed us how to get to the appartment from the Airport (20min bus ride) upfront and Reyes gave us a small overview on the town upon our arrival. Check-In was quite easy, and we were in close contact with her. Communication was easy! The appartment is in the very centre of Barcelona.
The room is small, but we were able to leave our bags outside of the room. I was there with my brother, I would probably not recommend it to couples who want privacy, but to Friends/siblings. The room is not made for staying inside so you should have plans for the day. Furthermore the walls are very thin and you hear a lot. People with light sleep might have some issues here.
Towels and bedsheets are provided. The bathroom is small but we never had problems with getting ready or crossing Carlos/Reyes/Mauro because we did not get up before 9am.
Very nice was that they had recommendations for places to eat or to visit.
Also it was no problem to come back home in the middle of the night.
Overall I would totally recommend staying with them. Again, thanks a lot! :)