Hi Lucy,
Mulligan Techniques:
Headache SNAG
Efficacy of a C1-C2 Self-sustained Natural Apophyseal Glide (SNAG) in the Management of Cervicogenic Headache - JOSPT – Journal of Orthopaedic & Sports Physical TherapySomething else useful: http://www.sld.cu/galerias/pdf/sitios/rehabilitacion/examination_of_the_upper_cervical_spine.pdf
If you havent heard of the Mulligan approach start reading now. Its very much a biomechanical-neurophysiological approach.