> She will be staying with me until such time as a repair op can be carried out
> The prospective family still want to wait for her.
If the advice is 6 months - as seems to be the case - couldn't the puppy go to its new home at the usual age? I have no experience of this situation but certainly if I were having the puppy I'd want to take her home as soon as she reached the right homing age. I'd also like
my vet to perform the procedure (partly due to travel and aftercare) BUT I'd also be willing to use my breeders vet if she thought it best.
From a buyers perspective I'd probably get a quote for the op (from both vets for comparison) and hope the breeder would reduce the purchase price by said amount but I appreciate this might not be a standard response. I have a very good relationship with my breeder and I know she'd trust me to do the right thing but I have known her for years and have had 2 pups from her in that time.
Perhaps some of our experienced breeders could help you word a contract or agreement to ensure that the puppy gets the required treatment and/or comes back to your vet for the procedure if you think it best