It'll be as sweet as fudge is.
The "not too sweet" thing provides no comparison. Fudge is freaking sweet. As candy-making goes, I don't make it much unless it's chocolate or peanut butter because it's supposed to be really sweet since the sugar is needed for it to turn out.
You can certainly make it without issues. Golden syrup is sold here, but you don't need it. Glucose is used in professional applications here. The ingredient for home is just corn syrup. The Brits are always trying to find substitutes for corn syrup for candy.
You can just replace both the glucose syrup and the golden syrup with corn syrup.
Why don't you make cookies if you're worried about things being sweet?
Or some of that salty sweet pretzel bark concoction everyone loves?
Or if has to be candy, chocolate truffles?