Im afraid to sort this out you are going to have to do loads of boil washes.
Set the washer going on its hottest wash usually 90 deg with no clothes in but use just a small amount of soap powder and set it going.
Now you will need to do this every other day for a week if you can.
Then do it weekly for a month.
Then just do it once a month and it will stop it from coming back again.
Now you can buy washing machine cleaners from the supermarket. These are good and if you get these do it once a month and this sorts this fault out.
Now the bits will go but its going to take quite a few 90 degs washes to clear it.
If you need anymore info just get back to me.
Thank you Daniel, your advice sounds good. And if it works I'll be very pleased and very pleased that I went to Just Answers for help!
Your very welcome. This will work but it will just take quite a few washes but it will go.