That's good advice. PIA Sports and I are through, at least the one on Manchester. They know for a fact that, most of the time, they are buying stolen discs and they refuse to go through the appropriate legal procedures for buying used goods. I've confronted them, told them that they are required by law to get an I.D., copy the license info, get a thumb-print and make the person sign a form that says that the items are NOT stolen and so on.
I have also had many very good trades and purchases in the marketplace at www.dgcoursereview.com. In fact, that is a great site. Check out their courses section - it has great reviews, maps and even some very cool features to let you track your scores and your own discs and so on.