Dont simmer on low heat for 5 mins, it needs longer (trust me i tried it again!) and it was too soft.

I think the trick is to get it to the 'hard crack' stage. If you think its ready, take it off the heat and drop a little bit into a glass of water - if it goes rock hard then its ready to add the bi-carb, if it sets soft then its not ready and needs more cooking so put it back on.

I ran out of syrup so when i go to the shops i'll try again - i'm determined to make this stuff whether it kills me or not - maybe 4th time lucky??? lol