I spent last year being very silly and buying 'fruit jelly' when I fancied it (ie whole raspberries in raspberry jelly, blackcurrants in blackcurrant jelly etc) so I decided to make some today. I used the Hartley's sachets of jelly crystals (non sugared), mixed it up according to the instructions and put some frozen rasberries in it. However, it hasn't set. When adding fruit do I need to use less water than I would usually use because of the water content of the fruit? Or should I have defrosted the fruit first? If this isn't it then what else could I have done wrong?