i owned a vectra b 2.2 sri, which i paid 5 grand for, and swaped for the z which my mother has owned for 4 years which she paid 7 grand for, its an import and its just about to hit the 60k miles mark. the mechanics are in great shape but the cosmetic side was a bit scruffy.
Ive cleaned it so much it now looks brand new but still has minor problems like the engine undertray has hit that many speed bumps its all bent out of shape and only this morning dropped onto the road whilst i was driving. not a big issue but an annoyance all the same, eigher way you look at it, its nothing for the sort of problems you would expect from a car hitting 17 years old now.
But like people said if you buy one which has been well looked after you wont run into any problems.