2 main engines inthe GTI:
AXX - first generation of engines
BWA - later engines
The AXX has a stronger bottom end compared to the BWA, but apart from some minor revisions to things there's little difference in the engines of note.
Common mechanical issues (use Google search for how-to guides on checking/replacing);
Pressure Control Valve (PCV)
Diverter Valve (DV)
High Pressure Fuel Pump (HPFP) cam follower
Common bodywork issues;
Rusty front wings - a known VW issues that can get replaced with 50% labour contribution (worst case) or completely free of charge (best case). Google it for more info
Make sure the DSG has been regularly serviced by VW, if not walk away as it's a large and expensive risk. Convenience and winter pack just give you more toys like heated mirrors, light washers, dipping wing mirrors in reverse and reverse sensors to name a few I think but I'm not 100% sure.
Above all else, make sure you drive it through the rev range so you can test the turbo and gearbox fully, look for smoke or any signs of gaps in power. To be honest, you'll know pretty soon if it's a lemon, but just take your time viewing it properly.
If you buy it, post up some pictures.
