Ditto to what everyone else has said. I am involved in independent rescue and the VERY vast majority of these reputable organisations distrust the RSPCA with a vengance and with good reason too. I could add reams to the other stories about their attitude and willingness to kill (the killing of the GSDs with a bolt gun is a campaign I am involved in), but it would take up pages.
Did you know that the RSPCA has over 119 MILLION pounds in the bank?
Did you know that the local branches are TOTALLY self funding, that not only do they receive NOTHING from the RSPCA HQ but also that they have to pay the HQ (on average over a thousand pounds a year), just to use the name RSPCA to help animals in distress?
My advice, from my own experience, would be to innundate the RSPCA with calls about these dogs, asking friends, relations and neighbours to call but most importantly follow this up with an email (making sure they know the exact address and postcode in advance and any pertinannt details or the RSPCA will say they can't do anything).
However you will get better advice and help no doubt from the organisations Greyhound Action, GreytExploitations (run by a wonderful lady who I know personally), and your local NO-KILL independent rescue (or any further afield). Please don't be put off by the forthright opinions of some of these - they really do know their stuff and they really do care.
To anyone who currently donates to the RSPCA I will say this - not so long ago I was contacted on the quiet by an RSPCA inspector begging me to help find a home/foster carer for a lurcher in an RSPCA centre as he was otherwise going to be killed.
His crime? Not biting a child, not being aggressive... he was just considered "too ugly" by the RSPCA to get a home and so they made the economic decision that he should die.
All too often, if you fund the RSPCA, you are paying for animals to die needlessly. If you are in any doubt, please read the article on the GSDs killed with bolt guns to see how they must have suffered.