I was baking bread for Thanksgiving, and the recipe called for 1 cup potato starch. I only had about 2/3 cup, and wasn't going to stop and run to the store, so I filled out the cup with arrowroot starch. The bread turned out fine, I couldn't tell a difference from the last time I had made it. I'd say, go for it.
I've learned the hard way to avoid ANYTHING that lists a generic ingredient like 'natural flavors' or 'spices', unless the packaging also specifically states it is a gluten-free item.
And at least here in the states, even if there is not an ingredient that raises a red flag, some candies are processed on equipment or packaged off conveyer belts that...