teropa,
Interestingly there does not appear to be any reference to migraine on the DVLA Medical Standards on Fitness to Drive
http://www.dvla.gov.uk/media/pdf/medical/aagv1.pdf
This is the basis for the medical requirements for the NPPL and implies that you could get an NPPL as a migraine sufferer. As you cannot fly at night, the visual impairment would not be so serious.
Best of luck.