If only spending £2k on the car, I'd be far more interested in the condition of the car than the cost of spare parts. That budget is pretty near the bottom of the barrel and finding a car worth buying is going to come down largely to how well previous owners have looked after it.

Also with that budget in mind, I'd assume you won't be wanting to travel very far for a potential buy, so it is also going to depend on what there is locally.

<< It can be quite shocking how rusty some subframes etc can be before they start getting noted on MOT's. >>

Indeed. But if a subframe gets seriously corroded the points it is attached to will probably be worse ?

Not always, bodyshells are pretty well sealed and protected, PSA cars from the 80's onwards have proved to be among the most rust resistant, its where wheelarches meet sills and such water trap points where shells usually start to corrode, particularly if the owner is typical in that they never give the undersides a moments consideration and wouldn't dream of washing the accumulated salt laden filth out once in a while, which bakes in hard during hot spells and eats the car away.

Sadly when it comes down to subframes suspension parts even full ladder chassis, if they get any more than a coat of black paint that's about the end of it, particularly poor at welds folds and seams, if hollow little gets inside, often there are sections presumably where the spray missed or whatever was supporting the part during dipping that sees no paint at all, even brand new vehicles showing areas of subframe and suspension/ axle rust already established before even arriving at the supplying dealer.