I don't know if you've had any success on the accommodation front, but I thought I'd tell you about my experience so others in the same boat may benefit.
For most of this month I have been in a cheap hostal room, getting colder and poorer as I have been eating out all the time. I have phoned countless numbers only to be told most times ´La habitacíon ya esta ocupada'
this has been with help of Spanish and English people resident here. (sometimes the best place for ads is in copy shops apparently, but unfortunately you cannot always tell how long the ad has been there....)
Anyway last Friday I took the plunge and went to an agency. They were able to fix me up on the day with an interview with a landlady who didn't mind the fact I was a) male B) English.
this organisation is called welcome to Madrid and are based on Calle de la Reina 7 (be careful in the streets between here and Gran Via). Basically they charge around 65 Euros for getting you somewhere, and if you view a flat and don't like it they will find you somewhere else.
End of the day I'm probably spending a lot more than 65 a week on eating out, so I thought the fee was well worth it.
There are other agencies that charge a similar fee and I feel it is worth it.
An English Bookseller in Madrid