We stayed at the flat for 3 nights at the end of January. It is in close proximity to Sagrada Familia. The place was cold when we arrived and it took a few hours for it to warm up. We put all the heaters on but we kept having the safety electric tap turning the whole electricity off so we had to turn some heaters off or not use other appliances such as microwave and kettle. The place was not what we expected. There was clearly a noticeable smell inside of cigarettes and mold. We had mold on the bathroom ceiling and probably that's what made it worse.
I would say that if you only need a place to sleep near Sagrada go for it otherwise better spend your money on a hotel or a place further from Sagrada.