1.9 tdi 130 bhp is the engine to go for and least problematic. My dad's passat on a 53 plate has covered 294k since he bought it new and is still as tight as a button and doesn't look tired at all. The only things that have been replaced are an alternator, rear shocks and 2 front suspension arms. All running gear is original and it still pulls very well!

When buying a car, I would say service history, condition and how it drives is more important than a number on a clock IMO. I've traded in high and low mileage ex fleet cars for 10 years and being low mileage doesn't necessarily mean you will get less problems