I can only recommend Andre's apartment !
André quickly answer to our questions, we had all the informations we wanted before our stay. In Lisbon, he warmly welcomed us giving maps, and several informations but also a special gift.
Concerning the apartment, it was very comfy with all amenities and all you need to feel like home, but also not far from Baixa-Chiado (tramway, subway, shops,...).
Just a detail, the ceiling is low so this apartment doesn't suit to people taller than 1m80, but we were not concerned by this point.
I really recommend this place which is in Lisbon center and allow you to visit all the city by foot !