Nice one pal, so you have not gone down the leasing route, like some, so it will be your car to do as you will,

mods ? I hope that's performance mods,

low milage MK6, your on the right path, how much detail do you have about the car your looking at, DSG/Manual, MY ? Leather/cloth ? FF satnav [ICE] ? Colour? Are you trading a car against the Golf.
Check for knocking when driving it, also if you can, ha! try to see if the wheels spin up on acceleration, possible Haldex problem, wheel kerbing, panels, scratches dinks, all could get a few quid knocked off, but it it's a dealer, they should have sorted all those issues.
Good luck with it.
Ps
If it's a low miler you should be ok with any problems, check anyway, make sure you strap that salesman in well. Ha!
