I had a very nice stay at Ale, Kunchok and Mikyo's apartment. It's an easy ten minute walk from Placa de Catalunya (if you take the bus from the airport, this is where you should get off). I printed out directions which was really helpful. Ale and her family were very welcoming and helpful. Kunchok helped carry my bag up (and down!) to their third floor apartment. The flat is in a great location. If you're a light sleeper it might be a little noisy at the weekend. I will definitely stay here next time I'm in Barcelona!