I've just had my machine fixed after the heater broke almost 2 weeks ago - hurrah!
I mentioned to the repair man that my machine can get a bit smelly and he said the best thing for getting rid of the smell and any dirt in the machine is 200g of bicarb in the drum and a 90c wash.
He also said that you shouldn't use vinegar as it makes the seals and plastic brittle.
So there you go, I thought I'd share just in case anybody else cares about such a dull subject 