Yes, it is. I used to buy it for my grand-daughter, who is Type 1 diabetic, but she is grown up now (20 years old)and doesn't eat it any more. It was made by Rowntree but not many supermarkets stocked it. I used to buy it in a supermarket locally called Wellworths but some of the big places like Tesco or Sainsbury might have it.
Robinsons has sucralose in, Rowntrees jelly is now sold as Hartleys. Jelly with no sweetening element whatsoever is going to taste of nothing, which I why I said buy gelatine and make your own.