I stayed here from 20th - 23rd March 2005.
Their website is
http://www.hostal-laplata.com/ I found the hostal easily – it is well placed (on Gran Via) for the main sights in the centre of Madrid and the room I had was of good quality. Here is the room I had.
Despite being close to the reception area it was quiet.
At night, there is no one on duty in the hostal but at the main door off the street, there is a portero who will take you up to the Hostal (on the 4th floor) and give you your key.
There is an elevator; the room was clean and fairly spacious for a a single and also contained a double bed. The bath and toilet facilities were on-suite. The room was cleaned daily as you would expect and clean towels were put in every day. The staff are friendly.
The entrance to the hostal is to the left of the Multiopticas shop as you look at the buiding. There are other hostals located in the same buiding.
Hope this helps someone.
Regards
Robbieroy