www.thetford-europe.com [UK]
www.thetford.com.au [For Austrailia]
Send them a question regarding this on their online 'Ask Thetford' page. If it is warrented then get back to the supplier armed with Thetfords reply don't forget to keep the origianl email to a from just highlight and copy what you send thetford then store in word file for reference, same wtih their reply.
Post the results in answer to your own question.
Bob, May 2010