We recommend you visit David Staveley's website on Sussex folk plays, which you can find at http://www2.prestel.co.uk/aspen/sussex/mumming.html. This is an excellent illustrated county guide, currently with 18 texts, external links to the websites of Sussex Mummers Groups, and a bibliography. The introduction covers the history of the plays in Sussex, and compares the different versions. In book form, it would sit comfortably beside the regional guides published by the Guizer Press.
David drew on earlier unpublished work by Dennis Outred of Ditchling Mummers. The site is aimed at a general audience, so it lacks the exhaustive references to fragments and snippets found in the more academic guides published by the TDRG. Nonetheless it is a valuable and very accessible source of information. Furthermore, the plays are only one of David Staveley's interests. If you go to his "Sussex Main Page" you will find similar pages on Sussex folkore and archaeology, including beliefs surrounding the Long Man of Wilmington, megaliths, and so on.