My parents and I went to visit Madrid for my mother's birthday, and we had a lovely time at Andrea and Daniel's flat. The flat is on the third floor of a lovely older building and the location of the apartment is unbeatable. It's located right in the lovely Barrio de las Letras, with loads of bars and restaurants, and within walking distance of great areas like Chueca, Malasaña, and Lavapiés.
Andrea and Daniel were very quick to respond to any questions and gave us great recommendations.
One tip for anyone sleeping in the living room: It gets noisy on the weekends because of the bars close by, so earplugs would be advisable. During the week the noise level is absolutely fine.
It's a great base for exploring Madrid!