Complex sentence: In the 18th-century changes continued with the building of handsome buildings with grounds, that were bought by merchants and bankers from the City and not infrequently by members of the Court and their'associations'.
Split into simpler sentences: In the 18th-century changes continued with the building of grand houses with grounds. These were bought by merchants and bankers from the City and not infrequently by members of the Court and their'associations'.