Try this site, if you haven't already.
http://www.aginsinn.com/
The American version was better since they gave the monsters more hit points, and put more spells in the original set.
It also spawned Advanced Hero Quest and then Warhammer Quest which also had a bunch of expansion packs of its own. People still make stuff for Warhammer Quest as well.
All of them were pretty cool games. The common thing to do was to seek out similar games with plastic heroes and monsters and cannibalize them for parts to use for your Hero Quest game.
