Hi Steve,
there are several fairs over the year.
One of the largest is in Dortmund in April and after May you have the "Modell Hobby Spiel" in Leipzig (30th sep - 3rd oct) and on later the year in Friedrichshafen.
For a detailed list just visit the site of Servonaut (
www.servonaut.de), they are listing all fairs on their homepage.