Allowing the RSPCA onto your property WITHOUT A WARRANT AND JUST LEGAL CAUSE is just like the people who aren't against the Dangerous Dog/Anti "pit" laws ... they think because they don't have a pit type, they don't have to worry about their own dogs being vilified. Only later will they realize that once one type is completely banned, they'll move onto the next, and the next etc etc etc.
It doesn't matter if you aren't doing anything wrong. It is up to them to follow proper procedures, the law is on your side (until the police get involved anyway).