Camilla, are you sure Withycombe's book says that Berengaria of Navarre's name was Berengière. I've always read that the French feminine form was Bérengère. Her maternal grandmother had the same name but in the Spanish form, Berenguela. As the royal family of Navarre all had Spanish names at that time Berengaria of Navarre may well have been called Berenguela as well.