Yes that's it. A fellow stands against a wall and cups his hands and someone else bends over and puts his head in his hands. Then a chain is formed and a whole team put their heads up the others arses. The opposing team jump on their backs and try to make them collapse.
Maybe that wasn't "British Bulldog ' but we called it something very different to "Strong Horses". Mind you this is Caerphilly were talking about: we talk different lingo up here lol.