Not sure if you're T1 or T2, but most diabetics with some experience would say leave well alone... it IS a nice thought, and having a little won't do you any harm, but generally, having a small amount of normal toffee won't do you any harm either and will be cheaper and won't have a laxative effect. Obviously if you're T1 you can adjust insulin levels to match whatever you eat, but if you're T2 it may be more problematic.
Moderation is always the way to go!