We had a great time at Cousins's place (the Explorer's Flat). The apartment had a great location (we walked everywhere) and everything that we needed. It was spacious, clean, modern, quiet. The Cousins replied quickly to all our inquiries and were very reachable. The apartment is on the fourth floor with no elevator so I would recommend it to those who don't mind this.
We would go back there again if returning to Lisbon.
Thanks again!