Looks like many of these Warwick Urns were made later on. This comes from a recycle site: -- Haven't turned up anything on the Aston Hall one.
"The Warwick Urn was originally a piece that was excavated in Italy by Gavin Hamilton and painstakingly rebuilt, a process that was both time consuming and expensive. This urn depicts a scene including eight gods. Legend has it that Lady Hamilton offended the restorer of the urn, so he changed one of the god's heads into a portrait of her with devil ears. This urn includes a base block measuring 27 1/2 inches squared. The classical beauty of late 18th and early 19th century period garden ornaments is here faithfully reproduced in composition stone and terra cotta, with painstaking attention to detail and the same spirit of enthusiasm that created the originals. The origins and history of each piece are studied and particular care is taken in faithful color reproduction. Some of the most elegant and illustrious hotels and houses throughout the world have bought these vases."