There a couple of reasons I can think of offhand to use corn syrup: for texture and to keep sugar syrup from crystallizing. Lyle's is a partially inverted sugar - don't ask, just go with it, like me - which it appears won't crystallize. You do NOT want your sugar to crystallize when making candy, unless you do want it to. I love to cook sugar; especially to make caramel, it's serious alchemy. Just make sure you have a candy thermometer, unless you know the Grandma Brown Method of dropping balls of hot sugar in cold water. With a thermometer, it's a piece of cake, I mean toffee. I recommend spreading the hot toffee on a half sheet pan (turned upside down) over a silpat.
1 1/4 cups organic sugar
1/3 cup Lyle's Golden Syrup
1/3 cup water or rum
8 ounces (2 cubes) unsalted butter, cut into pieces
1 teaspoon sea salt
1/2 teaspoon baking soda
8 ounces bittersweet or semisweet chocolate, chopped up