
Actually if they don't get their Rabies inocilation until 3 months of age they will have to be at least 10 months before being able to enter the UK.
First the pup must be chipped, then have the Rabies shot (if it is done other way around it will need to have the Rabies again). The Blood test cannot be taken until at least 30 days after the innoculation, and if it comes back with sufficent antibosy titre then the dog can enter the UK six months after that.