**sigh** this whole
GmbH thing again.... it's just the same as saying "Ltd" after a company name, so be careful what you're asking for... you could get the "Franz's Fickle Fibreglass GmbH" kit and the guy technically will have done nothing wrong.... 'cos you just asked for "GmbH".
Usually people saying "GmbH" are asking for the Votex GmbH or Quattro GmbH (used to be an external company, but moved in-house for the post 2003 "Sport" and now known as S-Line kit).
Votex = good stuff, but rare as rocking horse p00p... although there are a lot of replica versions out there..... just make sure you get high qual plastics and not some ropey glass-fibre mould or low qual plastics. Front Votex kits is generally regarded as one of the best aftermarket combinations of discreet, but agressive looks. Rear kit is a lot more open to debate - IMHO looks pretty decent if you're doing the rear pipes, etc to distract from the chicken-wire... but is pretty ropey if you leave the regular exhaust tips and plain rotten on the TDI down-turned pipes.
S-Line = OEM, so genuine parts are readily available, but about £1200-£2k just for the parts, so probably around £1750-£2.5 inc painitng and fitting, depending how complete you want the look: e.g. the S-Line embossed door sills around about £275 each now, but pretty pointless (only visible when the doors are open) and the proper top bumper is about £300, but the regular top bumper can apparently be modified fairly painlessly to accept the rest of the S-Line front, side skirt is virtually identical, do you want the door blades / rear spoiler, etc, etc.