The location is perfect, two minutes from Sol right in the centre of Madrid, and with a metro station just outside the building (we used it to go to the airport).
The room is very nice and clean. I have to warn, though, it faces a very busy street that is quite popular at night time. I personally had no problem, as I have a deep sleep, but the ones with a light sleep should consider it as it is very noisy during week end (my experience is based on a Friday night).
Charles was very responsive throughout the period of our communication. I didn't meet him though, his sister was the one to welcome us. She's been kind and informative, and very discreet, and we had the privacy we needed.