Full service history is a must, the miles are low but id expect atleast 3-4 stamps.
Get the bonnet up, oil should be golden and not black as 2 inthe morning. Also make sure the car is cold when you get there,
pre warmed cars hide knocks and rattles pretty well (phone ahead and request the car be left cold for you to inspect from cold)
Once the cars warmed it should idle freely without any pulpitations (i.e over revving without any throttle movement) Also make sure that when the car is revved to around 4-5k there is no dark smoke coming from the exhaust. Check the exhaust aswell, in standard form they are nothing short of absoluteley garbage (as i found out today lol) Make sure its rigid with little or no movement and the back box isnt visible from the back.
Upon test drive the car should be smooth without any steering issues, if when turning the wheel from lock to lock makes a knocking noise its likley to be the nut catching on the suspension turret, common place for the RS range apparently.
All the electrics should be kosher, the electric windows in paticular, The window regulators are shocking and give in pretty easily, they should go up and down freely with no drama.
Apart from general checks, the car wont be without its general flaws but body work should be resonably straight and dint free, if you can try and get hold of a paint reader, this will detect any re sprays on the paint due to the depth of microns (they should read a consistent 140-150 or there abouts) over the paint work.
This should give you an indication of crash damage in its life, also, HPi is aswell just to be sure its not a cut and shut >
www.mycarcheck.com