If you are ever told that the best way to make a small fortune in the wine business is to start with a large one, pause, smile briefly, then mention Tony Laithwaite, the man behind Britain's largest independent wine company: Laithwaites Wine. From a tiny warehouse under a railway arch in Windsor, England, Mr. Laithwaite and his wife, Barbara, have taken the most over-used cliché about the wine trade and turned it on its head, building an empire worth more than £350 million ($550 milllion).