The UK version is the version with the novella. Americans can also get the novella, but not all the time.
I don't think that the Belgian publishers thought it would be worth it to translate to dutch, seeing as Belgium (and Holland) is a small part of the gaming market. And you can't really sell an English novella in Belgium, because not everyone speaks English!
In short, the publishers didn't think the novella's were worth the effort.
Tovi 