The main drawback is if the cars 18 months old a main dealer wont want to buy it for stock because its an import
as the car gets older in my opnion it doesnt really matter much,
take 2 cars 4 years old 911, black, 12,000 miles, sat nav, sport design alloys, sunroof, sports exhaust, cyprus c98 import
4 years old silver, 25,000 miles, no nav, no sunroof, c16 uk supplied car
which would you rather have?
Some dealers will try and buy an import for a lower figure just because its another reason to pay a little less for a car.
But if you buy an import new it will be hard to sell if its 9/18 months old as the main dealers wont buy it and theres less specialist who buy nearly new cars as they're then competing with OPC's