From what I've read elsewhere, these are a straight convertion of 1 syn per 20 calories, so check the labelling on the packet. Although they're fat free, glucose is still sugar, they're probably quite high for what you get.
Yep ruthiebusybee is right, theyre just a straight 1 syn per 20 calories. Most sweets are fat free anyway (except chocolate) so the label is a bit of a con. All sweets are made of sugar - ie glucose, sucrose, fructose etc.