Trade-a-plane is a classic way to look for used planes. It's a U.S. publication, but you can use it to get an idea of what planes are available at what prices. (And they have planes from all over.)
http://www.trade-a-plane.com/index.shtml
It costs money to subscribe, but it is pretty cheap for an online subscription.
Also try this thread:
http://www.pprune.org/forums/showthr...ne#post1379994