We were welcomed in the flat by Renato's friend Felipe who was very kind and helped us with the luggage to the third floor (elevator wasn't working) and then showed us around the apartment and gave us advice about where to find a supermarket (there is a Pingo Doce right up the street, 5 min walk).
The apartment is very nice and had everything we needed and was just a short (roughly 7 minutes downhill) walk to the center and the Torre de Clerigos. We enjoyed our stay a lot and would definitely like to stay there again when we come back to Porto.