"A word of warning: The British are coming," proclaimed writer Colin Welland after accepting his Academy Award for writing "Chariots of Fire." Well, they may be coming over here, but they aren't going to movies over there. According to the British government, film attendance hit an all-time low last year. About 86 million tickets were sold, down by some 15 million . . . If you're going to be an artist, don't be an actor, says the National Endowment for the Arts. They've just compiled unemployment figures for all art-related fields, and while artists in general have a respectable 4.1 percent unemployment rate, nearly 40 percent of all actors are out of work . . . The woman wears a studded, black leather jacket, knee-high boots and chains. She's standing with ber back to the viewers, holding her jacket open and facing a group of about 2 dozen young men, all of whom march toward her with fixed, stoic expressions on their faces. But this weekly Variety ad isn't for a typically sleazy exploitation film, whatever it might suggest; all of these guys are wearing button-down shirts, loafers and pullover sweaters, and one carries a tennis racket. Now working on preproduction, producer Chuck Vincent apparently feels it's better late than never for his upcoming "The Preppies." Adds his advertisement-- "There's no stopping them."