We're both driving at the same thing.
Cancel the residential training - everything Spare says is right. It is never a good solution because to work a dog, in large part you need the incredible bond that training together over time brings, but primarily because it's not really the dog who needs to be trained. It's always the owner who needs the training.
Imagine sitting in a cockpit of a fighter jet and being expected to just 'work it'. You'd not have a clue where to start. Even if you'd had a lesson or two.
Your dog will be a bit like the fighter jet. Amazing, skilled, talented and responsive. Without training him yourself, you'll unfortunately probably be a bit clueless.
Sorry. It's clear that's not what you want to hear, but residential Gundog training is the lazy option. And the crappy one too. Cancelling it would solve the puppy problem.
And as a breeder, I'd not hold onto a pup for an additional 4 weeks. They need to start bonding with their new families from 8 weeks onwards. Missing that period is far from ideal. As an aside, I'd also be thinking very hard about allowing someone to have one of my pups who had created this sort of problem by not thinking things through. It's almost certain I would cancel the sale.