Benirras, in the north of Ibiza, is about as far as you can get from the fevered fleshpots of San Antonio. Here, at the end of a long and winding mountain road, lies a perfect slice of sand, bookmarked by cliffs and overlooking a deep, calm bay. In the 1960s, Benirras became infamous as the scene of drug-fuelled orgies. Today, it attracts a stylish mix of young Spaniards, Italians and Swedes