I had something similar - I think its called Restless Leg Syndrome? What I do to get rid of it is just to stretch my foot backwards towards me and do some gentle walking and stretching of the calves before I go to bed. What ever you do, don't point your toes when you stretch as this can hurt like hell!

Apparently taking an extra dose of Magnesium helps to control the cramping as well.

Good luck with it!