As suggested by the two ladies from 'How clean is your house ?'
Put washing soda in the drum and run the hottest wash.
(I put in a whole packet.It costs about 60 pence from any supermarket)
Then put a bottle of white vinegar in the drum and run the hottest wash again. ( The vinegar costs about 60 pence as well )
It cleans out all the gunge along with the smell.
You can buyer commercial products that clean a washing machine , but they are quite expensive and I don't think are as good as humble washing soda and vinegar.
Thanks for your tips I have tried leaving the door open but when I forget to leave it open the smell is there again even after doing a 90 degree wash. I will try the soda & vinegar, the only other thing I have read about is 'Purewasher' but that is from America, and quite expensive. Thanks again