Henry Winkler gives the thumbs up to a London stage version of his leather-clad king of ’50s cool. “Hey, he’s sensational,” Winkler said of South African actor Craig Urbani, who plays Arthur “The Fonz” Fonzarelli in a British musical based on “Happy Days.” Winkler is a creative consultant to the show, which opens today. He wasn’t interested in recreating the role himself. “I can dance, but I can’t sing,” he said. Oldie-but-goody songs such as “Rock Around the Clock” and “See You Later Alligator” are woven into the “Happy Days” plot, along with the original TV show’s theme song.