Teresa and her son Pedro are amazing hosts and very communicative and on hand with helpful advice and tips. They gave us tips for our stay in Porto, not just Lisbon itself! The flat is just a two minute walk up a very short hill from Apollonia Station, and just on the edge of the famed Alfama district, but surprisingly not noisy given the location.
It is decorated in an eclectic 'broccante' style with intriguing objects probably found in various trawls of the flea market just up the road (do go - it takes place Tues and Sat til 5pm). Teresa has equipped it well with masses of pots and cutlery, espresso machine, coffee, tea, condiments, ample towels and bedding etc. Beds are comfy. Wifi works, though we suggest making a quick check. Pedro is on hand if you need anything tech wise. Just note that the bathroom is a bit small, but we three adults managed fine (shower is large, but the room is a tad smallish).
The city was heaving with tourists in mid June during our visit but as I mentioned, the flat itself is quiet at night. If you visit in June, do stop at the street festa bar and bbq kiosks for local fare and a beer. At night, the locals emerge in just about every small square to claim back a bit of old Alfama and will welcome you as they celebrate their patron saint. Lisbon is an amazing city and we will definitely return to Teresa's place.