Rich foreigners visiting the U.K. have the chance to buy luxury goods at a discount given the pound’s slide against the dollar, making Swiss watches cheaper than on the continent. The Cle de Cartier Flying Tourbillon, one of the brand’s most expensive timepieces, costs $154,000 in the U.K., $15,000 cheaper than it does in France. EU citizens may need to act fast as luxury-goods makers usually adjust for currency shifts quickly to prevent such gaps.