PRESIDENT KENNEDY of the United States, who flew in for a short visit to England during his European tour, chatting to FATHER CHARLES DOLMAN when he attended Mass at the Lady of the Forest Roman Catholic Church. The church is about four miles from Birch Grove, the Sussex home of Prime Minister Mr. Harold Macmillan, with whom the President is staying. The visit to church was not without incident. A group of about 50 demonstrators had gathered nearby and carried placards, some of which said: 'Polaris. Take it back Jack'. Mr. Kennedy waved to them. He is due to leave Gatwick Airport for Italy.