I spent 6 weeks living with Lourdes and I had a very pleasant stay.
The room and the apartment were as described: rather small but offering everything one needs. It was always clean and Lourdes is a very nice host who always made sure I had everything I need and who gave me a lot of helpful tips with what to do or to see in Madrid. The apartment is very well located and connected. It is really quite, but still you have supermarkets, restaurants, bakeries, etc. nearby. The metro station is in a 5 minute walking distance and you reach the city centre in 30 minutes by metro.
I felt very much at home right from the start and I would recommend everybody to stay with Lourdes to explore Madrid!