Aw Fiona, my first cocker was a normal bitey pup, but was a complete ****
I resorted to putting a baby gate up and keeping him separate from us a lot of the time because he was litterally killing my son
When he became 8 months he changed, virtually overnight and is a total softee now. He did have a puppy tooth growing in the wrong place and causing him some pain - his biting, attacking and growling all stopped when his adult teeth were through. It's worth checking Duggies teeth are all in the right place, but even if they're not, the vets often recommend leaving them.
So feel for you I still remember the pain
Hannah x