
I know someone who has brought in a dog by this route. What you will have to remember is that the pup won't be able to come t0o UK until it is around 10 months old to fulfil the pet passport criteria.
It will have to be Microchipped before it has it's Rabies Innoculations with an acceptable vaccine. This will not be done until 12 weeks. Then a minimum of a month later a blood sample will need to go to the lab that does the titre testing for the scheme. If this comes back satisfactory, then the dog can enter UK six months after the blood test, with it's pet passport paperwork.
Someone in our breed had to wait longer to get their bitch pup in, as it failed the blood test twice, and so was over 12 months old by the time she could come in.
All the above means that either the breeder or a third party would need to be paid to keep the dog for this length of time, and the cost is likely to be similar, or slightly more than quarantine.
The advantage is of course is that the dog can receive training and socialisation.