The simple solution is to use Rapid Drip Former. These are pre fabricated drip edges which look exactly like felt and can be nailed to the roof so they are really quick and look great. I used them on my roof and got a very professional finish. Allot of roofers are using them now but they are a brand new product. Try www.rapiddripformer.co.uk for a demo
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix roofing.