Depends what year it is?
A popular mod is to upgrade the DV but this is more common on the K04 cars as it tends to be under more pressure. May be wise to get the latest revision from VW at £30ish pounds if its an early one. They crack under pressure resulting in loss of power. Latest one should cope easily on a GTI or you could go for the Forge option which is around £120 iirc.
Other than that its up to you really, alot of people feel the brakes arent up to the job with the extra power. Theres an endless list of things you can do to help with the extra power and to get the most from the car. All depends what you want fom it really and how much you want to spend.
Power:
Remap
Full exhaust
High Pressure Fuel Pump (HPFP)
Dbilas/Forge etc intake
Panel filter
Brakes:
R32/S3/Cupra R set up as they have bigger discs 345mm as apose to the GTi 312mm disc (fronts)
4/6/10/12 pots??
Then you have engine mounts, limited slip diff, coilovers, anti roll bars, intercoolers etc etc...I hope you have deep pockets being on here
Work at the tax office?? I Keep checking for jobs there, would be very convienient for me.
Clutch should be fine as long as the mileage isn't rediculous otherwise look at a Sachs if its manual. DSG are pretty good and will cope easily which also have a remap available for them.
Superchips are probably the cheapest option of the highest regarded companies mentioned.
HTH, Steve.
EDIT: with only 27k the clutch will cope with the extra power no problems but the DV could well be the earliest design. Someone will be along with the parts code but from what I understand it is a little difficult to get to on the GTI's
EDIT AGAIN: 06H 145 710 D (someone please confirm)