There was a plant stall at the Bowls Open evening and a very jolly lady and her daughter sold me and my daughter a Feverfew plant, which they assured us 'really works' for headaches.
I tried some last night for my bowls-induced headache and it really seems to work! I see from Wikipedia that it does indeed contain some active ingredients. It tastes nasty though - very bitter - but that's how you know it's doing you some good, isn't it? 
Feverfew