You don't say how old the puppy is, at the moment, but I'm guessing not yet 4-5 weeks old as you spoke about that as a possible second viewing...
>The breeder is registered with the Kennel Club so I'm sure is fine
Firstly, a breeder being registered with the KC means absolutely nothing. There are awful breeders registered with the KC and zero health testing is required to register puppies with the KC, so it means nothing whatsoever other than that your puppy is pedigree.
>Just seems quite sizeable given the pup is so young and hard to say if you will bond at that point (sure we will bond with him, more the other way round!).
I don't really get this concern, it seems very strange. There are reasons someone might not want to pay a deposit on a puppy so young but being worried the puppy won't bond with you, isn't one of them! You aren't going to see any signs of whether or not the pup will bond with you before you take him home at 8 weeks for starters, plus I've never really heard of people raising a puppy 'well' (ie not having multiple puppies at the same time) who've experienced problems with the puppy bonding with them. (And I'm a behaviourist and trainer...!).
However, the concerns I would have would be:
- if the puppy is very young (1-3 weeks old at the moment), that is too young for a reputable breeder to be inviting people onto their property to view the litter and to me would suggest there is something wrong/not reputable about the breeder. Baby puppies are very fragile at this age and disease risk is a consideration, plus a lot of bitches are very protective over the puppies at this age and you simply would protect the mother-and-puppies unit by keeping people away until the pups are a bit older. A breeder who doesn't realise this or doesn't protect the pups at this age, is a breeder lacking in knowledge IMO.
- puppies sadly often pass away in the first couple of weeks of life. There can be congenital issues that are not apparent until after birth, or diseases or infection - herpes, for eg. The majority of responsible breeders don't count their puppies and breathe a sigh of relief until after they're out of the neonatal period (3-4+ weeks old). Taking a deposit when they are they young, again to me, is not very responsible. I personally would be worried about what would happen should the pup pass away and would want in writing that a full refund would be issued.
- when pups are so small, there's no way of knowing what their personality, performance potential or showing potential is - so it's not really possible to match pups to suitable homes at such a young age. The breeder needs to live with the pups, watch them grow and develop and see their personalities and/or assess them in some way, to know how to place which pup in which home. If this pup is the only male pup in the litter, you are not going to get 'the best' pup for you, you will get this pup - whatever he happens to be like and however suitable or unsuitable.
To me it really doesn't sound like the 'normal' way of doing things and I wouldn't really be interested in working with a breeder who wanted 50% deposit on a neonatal puppy, frankly...