This is a good choice for a budget trip to Madrid. The communication with Enu was very easy and he allowed our friend to pick up the key in advance. The room was very clean and tidy with an en suite. Towels and toiletries were provided which is a great help when travelling with just hand luggage.
The room could however be improved massively with very little effort (filling in holes in the walls, fitting a proper shower head and fixing in the shower, for example). The bed was ok but not very big or particularly sturdy!
Overall, it's a good place to stay for the price and if you're not going to be spending much time in the flat.