Hi and welcome!
I'm surprised that the breeder gave you adult food, she really should know better -its a bit like feeding a baby steak and kidney pudding!
Its such an important stage in their development, -too much or too little of certain things can either make them grow too quicky, which is bad for joints, bones etc or stunt their growth, which can't be corrected later. I don't live in GB, so can't comment on brands etc but I'm sure there'll be lots of really good advice from other people on here.
Like Blueberry, I too am a strong advocate of raw but also appreciate its not for everybody and its also something you need to read up on a bit in order to undertsand the principles so you get the balance right. (Incase you're interested, I can strongly recommend a facebook group called Raw Feeding UK, which gives gives some excellent advice and support). But there are lots of excellent alternatives, my previous dogs had dried and wet food and lived to ripe old ages.
This forum is the best place for help and advice and I'm sure others will be along soon with more concrete tips. In the meantime, would love to see a few pictures!!