Bodywork will show marks easily owing to the paint colour, check bottom of doors around the sills and wheel arches for corrosion. Check all rubber on window surrounds for degradation.

When driving check operation of all gears especially engaging fifth, should slide in nice and easy. Check clutch operation a high biting point or stiffness could indicate excessive wear.
When accelerating check the IRMC is working, you should feel a subtle kick midway up the rev range, if it hesitates or wont accelerate smoothly its probably knacked.
Ensure the temp gauge settles mid way and stays there. Do all the usual checks for gasket leaks, take the oil cap off and ensure its clean and gunk free. Check the colour of coolant too.
Check a/c is cold, if not you may have a knacked compressor (worst case scenario)
Worth checking the engine code too. All ST200 engine codes begin with SGA.
It's either engraved on the right of the block, or, as in my case, on the black timing chain covers (I think) on the left, then you'll know it's an actual 200 engine and not the 170bhp lump shoved in.

Interior- usual wear and tear to be expected but check the operation of the trip computer and check the electrically adjustable drivers seat for normal operation.

Also check wheels for kerbing and inspect tyres for uneven wear, ST is hard on the standard brake set up, look to get a brake upgrade if you can.
Alot of Mk2 owners have upgraded the brakes using Mk3 calipers and pads along with 300mm ST170 discs.




*lot of this info has been copied from another forum I'm on