Service over. . . Chief Secretary Sir David Ford, who is stepping down as president of the Hong Kong Tennis Patrons Association, shows off the tennis memorabilia he received at last night's farewell function at the Hong Kong Club. Sir David and Lady Ford are returning to Britain at the end of the month. In his six years as president, the HKTPA's annual surplus has risen from $250,000 to a staggering $7.5 million. He has also made the Marlboro Championships into one of the world's top exhibition events and helped form the fund-raising Tennis Foundation.