Afternoon sun blazes on Pentillie Castle’s terrace above the sinuous river Tamar. Scores of cars ease up the drive. Ruth Watson would be proud. When TV’s former Hotel Inspector turned her attention from hapless hoteliers to grand houses (and their often eccentric owners), in Channel 4’s Country House Rescue series, Pentillie’s new occupants, Sarah and Ted Coryton, were only too keen to trade privacy for cameras and Watson’s no-nonsense business strategies for saving