About the flat: the flat itself was very satisfying, equipped with all the amenities you may need during a holidays stay. Both beds were very comfortable, and the terrace was a massive bonus (having meals outside was amazing!). The location of the flat, while not ideal in terms of proximity to the beach, clubs etc, was great in terms of amenities (several groceries stores nearby, including a large one) and is well connected with public transit (bus stops all around, and a metro station less than a 3min walk away - it is easy to get to the beach in less than 25min). The "un-central" location also meant that the street was very calm in the evenings, which is always enjoyable.
Overall I highly recommend this flat for a holidays stay!
About Sandro: Sandro was an incredible host. The first good surprise was that he offered to pick us up from the airport (for a reasonable fee) with our names on a piece of paper to make it easy to find each other (he also offered the same service at checkout!). Sandro was also very helpful throughout our stay, always responding to my messages within a few hours. He was also very accomodating at checkout, allowing us to leave our luggage in the flat beyond checkout until he drove us to the airport a few hours later.
Our overall experience was very positive, and we have already decided that, should we go back to Barcelona for another holidays (very likely!), we will book accomodation with Sandro.
Highly recommended!