How old is he? He looks about 6 or 7 weeks to me (pigment not filled in, small ears etc).
Never heard of an extreme apple head, and exhibitors don't really use the term apple it's either a good head or a bit plain normally.
I agree with Louise though, he doesn't look hydro but it is always something to be wary of in buying a puppy, heads mature with age do you don't want an overly large head as a baby.. Saying that I think his head looks normal.
The breeder should be stacking him by now, ask for a stacked photo and then you can assess from there. I would assume they show if his dam has her championship. You want to ask what the pups bite is (you want scissor.. Level is acceptable in the us but mouths move about and scissor is better), ask if his trsticles have descended (unlikely at his age) and what his movement is looking like. Get a pic of him free standing as well as it'll give you a far better picture than of them stacked as when you stack them we manipulate them to hide their faults!!
He looks nice for a newbie though but puppies can and do go off. He will have a fault, all dogs do you just need to be aware of that.
Also you'll get more respect from finishing your dog
Yourself over there. Handling is rarely done in the Uk so we all handle out own or occasionally well get a friend to handle if we're juggling dogs.