Jonny, make a shape with the pen tool around a third of that curve with the jaggies, then click motion blur... repeat on the other sections of the curve. See what that does...

that wont work, the motion blur will just make it look odd, it either needs to be realt sharp or the whole thing need sto be blured in which case a gausion blur would be mroe suited. a motion blur is to intense for these needs. it needs to be subtle, and then edited slightly to get rid of any 'over flow' useing a motion blur to the extent that it rids of the jaggies would add to must to the centre of the layer, which would look rather odd.