I did it.
I had another attempt at Lilly Pilly Jelly and it worked.
This time I followed Mariana's very specific instructions and made sure not to rush. It is amazing what can happen with a little more patience.
Look at the colour!
The texture is so much nicer than the first version. It holds together beautifully but without being too chunky. I managed to get about 350ml of liquid so I needed 350g of caster sugar, as well as the juice of one lemon.
Thanks, Mariana, for taking the time to give me such clear guidance.
Wishing you all a wonderful Easter.