Rubia,

when I got married, we rented at a place on Príncipe de Vergara, called Gerardo. That was nearly nine years ago (and in pesetas), so I couldn't tell you what the prices are now or what you get for them, but the place was reliable. I've found the address and number and a link.

Gerardo, Trajes de Alquiler
Príncipe de Vergara, 25
Tel: 91-576-1294

www.bodas.org/gerardo

Good luck, and let me know what the rates are there, just out of curiosity.