Again thank you everyone who posted advice for me. I was underfeeding my poor puppy, don't know why I didn't question the Burns RDA, it's clearly the wrong amount, certainly for cockers anyway. The interesting thing is, since I've upped his food amount, he's returned to being the calm, non-manic puppy that first arrived.
I'm going to continue with the Burns as I've got two 6kg sacks to finish but I've also added Nature's Diet to his meals plus chicken whenever I cook some. I've also dropped the weetabix & ham and his rewards are now his Burns dry food unless it's a high value reward, then I give him the dried liver. Plus I bought some milky bone biscuits but despite initially loving them, he's now lost interest. Going to get some gravy bone biscuits instead.
So in case anyone does a search on this, this is Ralph's new feeding routine (now at 10 weeks old):
120g Burns dry food (both mini and junior), 320-ish g Nature Diet puppy - I don't manage to get through the whole tub just yet.
I played around with the times to feed and found this suits all of us best.
8am Softened with hot water Burns dry food mashed into Nature Diet - generous amount
12pm Dry Burns with ND (smaller amount)
4pm Dry Burns with ND (small amount)
8pm Dry Burns with ND (generous amount)
9.30pm biscuits x 2
And sorry for TMI, but his poo's have remained nice and firm and regular.