“Batman” is winging its way to Britain, but youngsters under 12 will have to stick to comic books to catch the Caped Crusader. The national film board says the popular movie is unsuitable for children. The British Board of Film Classification applied its new “12" category to the movie that opens Aug. 11 in Britain. The category bars youngsters under 12 from a film no matter what parents decide. In the United States, the comparable PG-13 is only an advisory guideline for parents.