Have you tried Certo? It used to be available. Or you could try boiling it up again with some apples (leave the peel in in large pieces and remove afterwards a lot of the pectin is there). Bramleys are the best ones as they are sharp. Rhubarb Jam !!! Yummy.
Hi mom, Certo is available in the supermarkets usually in the sugar dept and Silver Spoon make a powder pectin which is brilliant the only problem is not always available only certain times of the year i,e when all the summers fruits are around I tried to find some in April to no avail.