We stayed at Central Downtown Appartment for a long weekend in September and had a great time. It's located just in the city center of Lisbon with all sights, restaurants and bars at easy walking distance. A small supermarket can be found on the ground floor of the building. Conveniently we could deposit our bags at the appartment just after our arrival (due to cleaning check in was only after 3pm) and were also able to leave them there until our late flight back. Big thanks for this service!
All in all my fullest recommendation for any group wanting to explore Lisbon!