Jeanie you may be aware there are very strict rules in place for transporting dogs to the UK. One in particular requires a six month waiting period after the dog has been given a rabies vaccination and then given a blood test to insure it's effectiveness. Another is the requirement of an international microchip. If the dog is chipped with one that their scanners can not read, you must either supply a scanner...or the animal goes in quarantine.
Here's a link if you haven't already researched it.
Defra, UK - Animal health and welfare - Pet Travel Scheme - What you need to do to bring your pet into or back into the UK under the Pet Travel Scheme
hth.