my mk5 is a cat D also, The part you need is a Front panel, you can pick these up second hand or brand new, I would suggest brand new, as it wont have any cracks, genuine can be very expensive, so the other brands should be fine, just choose a reputable company ( I think euro car parts sell them for £100)
The gti bumpers are different, and do have their own front panels, if you're buying a new one, best to get a gti front panel as it'll have the correct mount holes for your gti bumper!
Make sure you car doesn't need any pulling or anything like mine did, best thing to do, get a new front panel, new headlights, stick to genuine oem headlights as they allow for adjustment in the mountings, I found this out the hard way with some depo headlights.
check the rad pack lines up nice along with a new belly pan of course as mine doesn't and it causes problems for my splitter.
I would personally trial fit myself, also remember the whole front panel can move up and down and that can make a huge difference to the way your bumper sits, I notice many gti conversions even show cars, the front bumper sits lower, and causes a gap between the bumper and the headlight on the bottom, looks horrible as stock gtis don't have this
hope any of this helps