So early in June I sent HMRC the following:
1 form SA400
3 forms SA401
3 forms 64-8
Only sent 3 64-8s as we already act for one of the partners.
Nothing happens for six weeks until today I receive letter from CAAT - ''sorry we can not deal with the enclosed 64-8 you sent us unless you enclose either forms SA400, SA401 or SA402!
No phone number on the letter and of course no way that I am aware of that you can ring the CAAT to ask them to sort themselves out.