I used the River Cottage one.
I wouldn't worry about it too much, as the ingredients aren't an accurate science. It will just slightly affect the final taste, a bit like modifying beer recipes.
Makes sure you use decent bottles else they may explode when they carbonate!
I forget if I used 6, 9 or 12 heads of flowers in the gallon, but I tasted it as I went. I used 1kg of white sugar and the juice of one or two lemons to taste. Use a champagne yeast.