LONDON— Tourist visits to Britain in October plunged by nearly a third, official figures showed on Friday, Dec. 7, as the September 11 skyjack attacks piled woe on a tourism sector already hit hard by the foot-and-mouth outbreak. Seasonally adjusted figures compiled by the National Statistics office showed the number of people arriving in Britain for holiday in October fell to 554,000, 30% lower than in September and down 30% from a year ago. Visitors from North America, the target of the September 11 attacks, fell the most sharply, plunging 39%, compared with a year ago. Western European visitor numbers were down 27%.