Use cane sugar not beet
The jam does not set properly with beet sugar. It needs to be cane sugar. Use Tate and Lyle.
Not good results use Tate and Lyle 1:1 jam sugar!
Used this to make jam twice now as it was the only jam sugar in my local tesco. Tried it with blackcurrants and plumbs to make jam , both times didnt set well, I dont think there is enough pectin in it. Have used Tate and Lyle 1:1 jam sugar(1kg sugar to 1kg fruit) before from Tesco which worked perfectly every time. Will not use this sugar again and will seek out the Tate and Lyle product from another supermarket that stocks it.