I believe figures have shown that there are currently more staffs in rescue than any other breed, even mongrels. They are being overbred by irresponsible owners who think it will make them money, then sold to other irresponsible owners who do the same. They then start to grow out of the cute puppy stage and become very difficult for inexperienced people to manage, they chew anything and everything as they have powerful jaws and although they seldom start a fight with another dog, boy can they finish one. Sadly they have become a status symbol for certain types of people. In the right hands they make excellent family pets, if bred and reared and trained correctly. They even have the nickname of the 'nanny dog'.
Choose your rescue carefully, one of the breed rescue societies would be your best bet, rather than an all breed rescue home, as they are run by people who are experienced in the breed will be on hand to give experienced advice. The Kennel Club has a list of breed rescue societies tel 0800 6066 750.