It's thanks to William that The Price is Right came to the UK. He single handedly hyped up the audience to lose their typically British stiff upper lip and to go crazy for the prizes.
Though the man himself recounted it differently - he said that the idea that British audiences wouldn't behave like the US audiences was rubbish, in part because of what he saw during his time as a Redcoat, and in part because of how people behaved during The Last Night at the Proms. He said that the warm-ups including airline style safety warnings about fire didn't help the situation.
There's a story about him hearing Land of Hope and Glory being sung for someone's birthday while he was out for dinner, and deciding to use that for his warm-up, which worked brilliantly.
He also said that having large groups (another thing he learnt from Butlins) helped break the ice, so he made sure audience was mostly coach parties.
EDIT: All this information and more can be found in the earlier-mentioned Louis Barfe's book
Turned Out Nice Again: The Story of British Light Entertainment
. It's 189 pence on Amazon for the digital version.