Hi again everyone, thanks for all your comments and suggestions, I'll try and answer some of your questions.
Amanda - Yes we got her at 8 weeks. She has had lots of socialisation with other dogs, we do two puppy classes a week at the moment and she meets lots of dogs on her walks, she has been having one short walk and one longish walk per day.
Amanda/Helen - I'm wondering if her diet might be the key to her problem actually, when we got her the breeder was feeding her Natures Menu which is a raw food, (I wonder if its similar to BARF?!) I was told by almost everyone to start changing her over to dry food so I bought some James Wellbeloved and gradually starting adding it to her food. After a while she seemed to go off her food. I thought she had gone off the wet food so I changed over to different wet foods to find one she liked, cant remember what they were but I wonder if that was when she started having these frenzies, maybe I mixed it up too much?
A few days ago we were recommended Arden Grange which I used yesterday and this morning, had to add loads of water to it to soften otherwise she wouldnt eat it!
It was quite funny actually, I gave it to her dry and she turned her nose up, I added some gravy and softened it down and offered it again and she walked away, I had to actually feed her from a spoon until she realised it was soft again and started eating it herself, I had to laugh it's just like having a new child!
Anyway (and if anyone is still reading and not fallen asleep I thank you, lol) she only had one frenzy yesterday and it didnt last as long, but I also tried what Newbie suggested and told her to sit and offered her a treat and it worked, she went back to the biting again but was aware enough to stop for a second, which I was pleased about.
I'll see how it goes today, we dont have any other problems with aggression, I can groom her, take her food away etc with no problems, the trainer thinks she is just taking puppy biting to another level and that normal training will eventually work.
Thanks for your support, I'm so glad I posted because if nothing else I realise I'm not the only person that gets stressed and upset and ends up in tears at the end of the day!