Jez, a good thing to add to your 'piking' arsenal are some of these http://factory.dhgate.com/product/morn-sun-scrapbooking-rotary-paper-trimmer-5-cutters-easy-cut-p842003.html
Designed to be used on a special bed / ruler, they work fine freehand against a metal ruler, or on curves. Perhaps not as sharp a cut as your pinking shears but may be useful?
Richard