how can I fix my Hotpoint Ultima WT721 washing machine?

my washing maching is a few years old and works perfectly well, however recently it has developed a really bad smell inside the drum. I have cleaned around the rubber door seal and run two 95 degree washes to try to clean out the inside. But it still smells really bad. It drains fine so there can't be a blockage. I have no idea what has caused this smell but it is coming through the holes in the drum.
Any ideas of what I can do?