British movie star Googie Withers has chosen an all-white bridal ensemble for her wedding today. She will marry Australian-born film actor John McCallum at St. George's, Hanover square. Her longsleeved dress of white satin brocade has a deep, round neckline, with a stiffened Bertha collar. The dress has a full skirt and a deep train. Veil of French tulle will be held in place at the side by white hyacinths and orchids. Her only jewelry will be pearl and diamond earrings, a wedding present fro