Antonio and his family were the bestest of host one can imagine. Enmaanuel, his son, provided with information on how to get to the appartment from the airport. He even picked us up personally though we were quite late. In addition, he gave us some nice tips on where to eat and what to to on New Year's Eve. But the nicest thing was that we were given some nice chocolate and fruit.
The appartment is great for four people to stay there. It's very close to a metro station, so access to the city centre is as easy as it can be. It's located in a lively neighourbood with some nice restaurants nearby. Shopping facilities to get food and the stuff you need is just across the street.
When I come back to Madrid, I will ask Antonio and his family for their place!