[Margaret Pilkington]

Heth, run a hot wash(above 60) with the machine empty..........a capful of bleach would be good.
On the last rinse Mix a dessertspoon of bi carb with a small amount of hot water and put it into the soap dispenser of the washing machine.
Once you have done this, and the machine has finished its cycle and has stopped....take out the soap drawer and give it a good wash in soapy water(washinp up liquid is fine).......when it has had a good wash put some bleach in the water and leave for about 15-20 minutes...this should kill and mould(which is what the black bits are)
Give the drawer a rinse and put it back in the machine.
Try to dry out any residue of water that collects in the rubber seal, and leave the door of the machine open just a little bit.

This routine may need to be done every few weeks. But ditch the low temp washes........and try to wash something at a high temp each week(towels are fave...or pot towels.....I wash these separately because I don't use fabric softener on them...for the reasons that Kate stated)