Hugo and Ioannis's flat is a fantastic place to stay in Barcelona. It's quiet, right to the centre, and they prepared us complementary fruit and chocolates. Ioannis was also very friendly and helpful when we spoke on the phone.
That said, it's worth mentioning that the flat is very old. You have to climb lots of dirty, very narrow stairs to arrive, and some floor tiles of our room were loose. In addition, the walls were very thin, and several times we were woken up in the night by people having parties and listening loudly to music.
I'd recommend Hugo and Ioannis' flat as a central, convenient place to explore Barcelona!