There are many more tuners on that side than over here, no doubt due to the greater percentage of diesel cars there than here. Superchips have seemingly been around forever, but there are many others (Tuneit, TuningBox, Powerchips) that may have what you want as a price more to your liking. Pick up a copy of a diesel performance magazine to be bewildered by the selection you have available, that we can't get here.
Do you want re-flashing through the OBD port that requires an appointment? or would you prefer a plug in module that comes in the post?
Customized specifically for you and your van, or off-the-rack generic that works in any VWAG 1.9 regardless of vehicle mass or Cd?
What revised level of output do you want?
We can't answer these for you. You'll have to shop from what's available.
Come here and we'll have recommendations of providers based on our own experiences, but those for us that meet the pertinent US requirements may not be appropriate for you.