Basically, what's gone wrong is a simple UI mistake.
if you tap N in object mode, you'll get the transform properties window that'll show over your active 3d window. On the window, there's three different modifiers, rotation, scale and location, as long as you're in object mode, the Scale property will actually effect the final model outside of actual placed verticies.
So if you have it set to 1.000 all around, it's going to export exactly 1-1 as you see it, if you have it at 0.5, it's going to expand when exported, because according to the object, the vertecies have been shrunk to fit the current state, and anything above 1.0 will shrink the model, since the verts are being enlarged to get to the state they're in in object mode.
so anytime you scale anything, be sure that the scale property in object mode is set to 1.0, and do all your scaling in editmode, which scales the verts themselves, and not any object settings.