I think it´s not that easy, if you ask for whole Europe. Most people are working with military-models or planes
so it is hard to find some car-fanatics.
Biggest show in Germany i would say is the "Intermodellbau" in Dortmund. You will find producers like Revell there as well as private model-builders.
If you never have been there, it´s worth a visit. Take a look:
http://www.westfalenhallen.de/english/1907.php
Ok, right now i see they call themselves "biggest show in Europe" - maybe!?
Furthermore a heard Jabbeke in Belgium would be really nice, but i hadn´t have the time to get there yet. You will find some pictures here:
http://www.gb-scaletrucks.de/main_eng.htm
Do you have any further information about "AMT-Torrent"?