Complex sentence: The stretches of the two continuous streets have several different names, however all but three of the names (Swift's Row, Bachelors Walk and Usher's Island) share the same "Quay" designation.
Split into simpler sentences: The stretches of the two continuous streets have several different names. However, all but three of the names (Swift's Row, Bachelors Walk and Usher's Island) share the same "Quay" designation.