The breeder is responsible for registering the litter.
Both parents of the puppy must be already registered with the Kennel Club for any of the pups to be registered. Really the bitch's owner should have had a form from the Kennel Club at the time the mating took place as it needs also to be completed & signed by the owner of the stud dog.
Were you given any reason as to why the puppy hadn't been registered by the breeder? You should only really need to transfer ownership of the puppy at the Kennel Club, simple enough but you still have to pay.
I've never sold a puppy without registration papers, so I could be wrong, but I think only the breeder can do the initial registration. I should ring them & try to find why they didn't & if they would still register the litter.
Here's a link to the relevant part of the Kennel Club website
http://www.thekennelclub.org.uk/item/346