There is a desensitisation course for RAF pilots that has considerable success with motion sickness.
Always worth making sure that you don't have the heater on too high and if you have supplemental O2 in the cockpit, that can help as well. I remember on a Hawk flight, the pilot (I was on a jolly) sneaked the heater up a bit before the aeros and I felt much more green than I usually do.
Sea Bands work well for some. I can't prove the science but if they work then great and they are less than a tenner at Boots (and you don't need to tell the CAA!)