A well-furnished, generally quiet flat in a residential area a 30min door-to-door trip into the centre. Eduardo was generally very helpful, but there was a brief problem when he got the date of our departure wrong. Otherwise the flat was fine, and we loved Madrid.
Two quick tips which make the flat nicer:
1. The 15min walks from Puente de Vallecas (up Pena Prieta) or Estrella/Vinateros on the Metro are nice. Don't do the walk from Neuva Numancia (which Google Maps recommends), which is less nice.
2. The flat was quite dark when we arrived as there is only one window. It lightens up if you open the solid door, and instead use the second, see-through front door when you're in.