We had a lovely stay at Marta's flat. It's on the doorstep of two metro lines so it's very convenient to get around town, close to Barcelona-Sants station (walking distance) and enough space for two adults to spread out. There were also plenty of food options and supermarkets nearby, and the kitchen was stocked with plenty of tea and coffee. Laundry also had detergent!
Only thing to note is that there is one flight of stairs up/down to the door so if you have heavy luggage just something to keep in mind!