I've never heard a slide whistle referred to as a Swanny Whistle. If you're looking for a great example of slide whistle playing, check out any recordings by the Hoosier Hot Shots. The washboard player, Hezzie, is the best that I know of on slide whistle. He trades licks with the clarinet player in the band and plays leads that are mind boggling.

He's also one of the best around on that ol' Hootenanny (washboard/sound effects gizmo) of his.