We spent two nights in Javier's flat. It was clean and convenient (there is everything you might need for your stay, bath products or kitchen-wise.)
The district is close to Espanya Square, but note that the nearest station is a suburban train one and you'll lose a travel credit for just one station (you'll need to validate another ticket at the metro in Espanya Square.)
Javier left a Barcelona guide at the flat which was great because we forgot ours at home !
It was overall a nice stay, however he was very insistent about us leaving before 11 AM (two messages the day earlier, and one text at 11.30 to check is we were out of the house, with no reply when I answered thanked him for his flat. This leaves a mixed final feeling)
But good experience! I definitely recommend.