It might have been cheaper for Heidi Montag and Spencer Pratt to buy new clothes instead of having their old ones dry-cleaned at the Dorchester in London. The dim-witted reality-TV couple from MTV’s “The Hills” was across the pond taping “Celebrity Big Brother” last month and staying at the super- luxe Park Lane hotel owned by the Sultan of Brunei. Back home in Carpinteria, Calif., Pratt told Montecito Journal columnist Richard Mineards, “We didn’t have any clean clothes left, so we sent a bunch of laundry to room service . . . but we were totally flabbergasted when we got the bill . . . £3,500, around $5,000.” After balking at first, the TV production company reluctantly picked up the tab.