Trev,
In the absence of any other suggestions here is my theory.
Unlike normal railtours that just have one or two advertised locos, "Spin and Win" railtours always employ quite a few different (often freight) locos.
I believe that "Spin" is gricers slang for a trip-out looking for unseen locos and I assume that the "Win" element comes into play when you "cop" one or more of the locos hauling the train.
Just an idea.
