"The charity mainly uses labradors, golden retrievers and crosses of the two breeds."
Ah, methinks another reason to return to the good ol'days of German Shepherds. ;-)
Why cuz no one would try to bite one? :~D
They're still used... Lots of assistance training programs had to move away from GSDs only until the breed gets their hips back in shape. They can't afford the risk of wasted money, time and training on displastic dogs. I ~think~ GSDs are on their way back to soundness, but it's been a long haul.