If you are buying from a dealer, should they not be offering a warranty with the car in the first place?
This. Sale of Goods Act basically forces dealers to to take some level of responsibility, so almost all provide a warranty on pricey second hand motors. Even at the the £2k end of the spectrum, you tend to see "if the gearbox or engine goes within x months, we'll fix it".
I looked at some of the warranty companies last time I bought a second hand car privately, and the exclusions list was daft - if I recall correctly, clutches (fair enough, given you can abuse them to death), flywheels, turbos and engine valves were all excluded, and they're all the bits I was worried about on a petrol turbo, I didn't bother.