I've just had a workout in the Workspace Editor. Doesn't seem to matter what workspace I'm in, or what menu I place "Document Windows" under. It just doesn't work. You click on the Number 2 document that is open but you still see the Number 1 document. However, if I place "Document Windows" under the second last menu in the Workspace Editor, "Document Context (right click on document)" it works fine. So now all I have to do is right click on the visible document, up comes the list, and then ping on the other open document I want to view, and voila... probably more convenient than ever once I get used to it. But pretty wierd that it doesn't work under a normal menu. My other programs work fine in that respect... could just be my setup.
So thanks to all of you who gave advice. I'm happy with this solution and can get on with my work again with a bit less frustration!