Hola Scampy, Typically auctions are not part of the Spanish property sales culture. Several British companies tried to start property auctions a few years ago on the Costa Blanca but it seemed to sink without trace. There was I believe talk of legal problems with auction selling.
Banks will as a last resort dispose of any re-possessions via an auction, which never seem to get any publicity and are very Spanish affairs, but usually they are sold to contacts the bank manager already has established.