A true gloss black, as is found on the various trim pieces on the exterior of the Golf, is pretty universal. Just ask for a pure black (some "blacks "are actually dark grays, or contain small amounts of blue, purple, or brown). Any automotive paint shop will know what you're asking for--especially if you tell them that it's to match some exterior trim pieces. A really good shop will have a tool to measure the color of the original piece and duplicate it exactly. Besides, as long as there aren't any metallic or opalescent particles imbedded in the paint, you ought not to notice any differences between a freshly painted piece and one from the factory, provided that each piece has a clear demarcation line (not a blended overlay). The edge line on the panel will fool the eye to miss any infinitesimal differences in the shades of black. But whatever you do, get an automotive grade paint; else, you will see a difference after a couple of years in the sun.
However, if you're looking to emulate the gloss piano black on the interior, make sure that you give the piece a shot of clearcoat, which will add to the sheen. If you are doing something with the interior, I'd suggest painting all of the contiguous surfaces, that way any slight differences will be absolutely invisible.