From the top:
There are 3 good GTIs left in the UK. Your mission should you choose to accept it is to find one of those three cars and purchase it.
Most GTIs have been smacked and most are thrashed.
Your job is to try and limit the amount of crash damage it had, and figure out what type of wally was last driving the car.
You are looking for any panel that doesn't match. Check out Golfs that you see in garages and on the road. The panel alignment should be perfect. No question. If the panel alignment is not perfect then its a pattern part (eg replaced) or its a real part that doesn't quite fit the body. Ask yourself why there is a panel part or why its not fitting.
A good place to look is on the front doors, between the door and the front wing. Follow the gap right to the bottom. You'll now be looking a piece of foil (black foil). This foil should be perfect. It should not be broken.
If its broken then the panels are old and there is something (eg rust) behind the panels, or someone bent the front of the car at somepoint.
Check the interior wings inside the bonnet. They should be the same colour as the outside wings.
Check the colours of all the panels. A resprayed panel will age and fade at a different rate than original panels.
Check the rear panel. Have a look inside the boot (and the panel) and see if its been beaten out.
A good one to check (only recently found this), on the rear panel below the centre VW badge (if '88 onwards), there is an indented line, that the rear bumper fits into. This line and the bumper should have perfect alignment throughout the length. If not, then the rear panel didn't get beaten out enough when pranged.
Another place to check is the alignment between the front doors and the windscreen. The gap should be consistent. If the top is less or more than the bottom - then walk away. Or run. This would be a heavily hit Golf.
I am NOT saying that a crashed Golf is a bad Golf. But if its been crashed then you need to know. Forget everything the owner tells you.
On the engine, check for smoke.
Take it for a drive. If the gear stick doesn't go into a gear properly, then its worn big time. The gearboxes are sweet, they will guide you through the gears. If it guides you to something that is tough to get into gear - its been thrashed.
Have fun.
Tin