Our stay at Helena's place was very nice. The apartment is very clean and good looking. It had everything we needed for a pleasant stay. The apartment is quite close to the center.
We didn't meet Helena or Artur personally, however two of their colleagues waited for us in front of the building. One of them helped us settle in the apartment. She also provided us with a map of Porto and told us where to find everything we needed (besides the tourist locations and how long it takes to get to them, she also told us where we can find clothes shops and supermarkets).