When you get to the screen from which you select your flight click on the flight number. The pop up box shows aircraft type and, right at the bottom, the selling class, which is price dependant. As Globaliser has said classes Q, O and G attract reduced their points.
My gripe is that when booking you are only offered the then current lowest fare. You can't opt for the "max reduced tier points" (if you see what I mean). On my regular "shuttle The difference between Q class earning 5 points and the next class N earning 10 points is only £6 which in tier point terms is excellent value.