If it is at 40k, has it had the 40k service done - quite a big one. Is the car manual or DSG - DSG oil needs changing at 40k. If it has been looked after well and been tracked it may have been changed early - check the logbook, if it has it's a good sign of a caring owner! If it has been tracked, check brake set up carefully - rotor/pad wear. Some early GTI's did have steering rack issues so check this out too. Go through all electrics thoroughly for piece of mind, check boost/dv. Ideally if there is someone with VCDS get them to scan for codes when viewing car, doing some logging if a test drive becomes an opportunity. Not sure what the interval on the cambelt is, seems a bit early? Am sure others will step in.
