As for buying UT2004, you could buy a digital edition from:http://www.gog.com/en/gamecard/unreal_tournament_2004_eceOr if you want a physical product, you could get Unreal Anthology (from the site you posted above) - it includes Unreal, Unreal 2, UT99 and GOTY. Or look around more, I'm sure there's places where they sell UT2K4 in Netherlands.
YAY! Now we can be gog buddies!
Just remember that we share the same version of UT2004