Can anyone recommend a brand/supplier of good Peony cutters?
Any help or advice will be greatly appreciated.

Global sells several sets of cutters. I like the Sunflower ones here

http://www.globalsugarart.com/product.php?id=19118&name=Peony%20Cutters%20%28FV-048%29%20by%20Sunflower%20Sugar%20Art

or the ones by Colette Peters a few items down. You don't really have to have specific peony cutters, though. In one class I took, we used different sizes of rose petal cutters and used the point of a smaller petal to cut little V-shaped indentations on the outside edge of the petals and then gently frilled the edges. Worked like a charm.

I have the ones by Colette Peters (its a set of four cutters). I have no experience with any other peony cutters but I really like these. Instructions were fairly clear and the flower turned out well even though it was the first one I tried. Here is a pic:

http://cakecentral.com/modules.php?name=gallery&file=displayimage&pid=1715166&sub=1715167