
I generally respond on the lines of the following:
All my puppies are spoken for, but you will find that people will only sell abroad if it is to someone they know, or recommended by someone like that.
Alternatively if someone is involved 'in dogs' (showing, etc) if they can get good references from a canine club, as to the potential owners character, experience, and standing in the canine world, references from someone in the UK , and references from their Veterinarian, then someone might just consider it.
As you can appreciate once sent abroad, if anything goes wrong with the home there is nothing the breeder can do for their babies, in UK there is always the option of having the pup/dog back, if things go wrong.
Also there is the issue of cultural differences in the standing of Pet animals in many countries and lack of welfare protection laws.
You can get a good idea of the likely costs involved with shipping a pup from here:
http://www.overhill.co.uk/exports/index.htm who buyers of my pups have used.
This will usually weed most out, especially when they realise the costs involved with importing.
If they are willing to jump through a lot of hoops then I feel serious consideration is merited, after all I expect to be able to import from abroad (numerically small breed only kept viable by regular imports).