I bought some Dettol mould and mildew spray which contains bleach and donned my marigolds and sprayed the whole drum and the seal. It is not meant to be used on rubber but I decided if this didn't do it I would replace the seal. I shut the door and let it get to work and ran it on an empty cycle.
I am amazed at the difference. It has certainly cured the mould for now and it smells so clean.
I should have remembered this product as I have used it before with great affect on bathroom mould when we moved into our last house.
Definately reccommend it, although not not an eco product, but maybe a strong cleaner is required every now and then to keep these things at bay.
Thank you for all your advice