If the key to a nation's priorities lies in its shopping lists, then Britain has been transformed in 50 years from a society spending mainly on basic food and warmth to one transfixed by the delights of leisure and travel, new figures show. The usually stern face of official government statistics softened yesterday to offer an anniversary glimpse of family spending habits in 1957, the year an annual household expenditure survey was first launched in a post-ration book Britain.