Personally I wouldn't buy a car from dealers, be they expat or local, as I am quite willing to source my own cars direct, based on my own mechanical knowledge.
Doing this will generally save between 30% - 50%, and 9/10 you have access to the service records if you have a preference for 1st registered owner cars. After that, the maintenance records, seem to magically disappear, likely the odometer has been hair cut, with no real way of proving what needed to be done, especially where close clearance heads apply and vital cam belt changes every 80,000km, if ignored, piston meeting open valves the result, pretty much bricking the motor.
Generally Andrew from the car locator is quite expensive, there are much cheaper alternatives around, he's like one of those fish that feed off sharks, most of the local car trade knows him, ie Tommy Siu of Vins, Vincent Chan, and so on, and so on... If lazy and willing to pay higher than local market rate, buy via this route.
The expat classifieds are generally good buying, as owners , generally provide service history from HP Cars or Sun Hing with a detailed compliment of maintenance receipts as to whats been done to the car.
Feel free to ask as many questions as you want, WTBhotia and myself are pretty knowledgeable, I have bought, sold, shipped abroad, over 20 cars since we lived here.