Updated: May 2011 - The Elderflower Champagne recipe worked brilliantly. It's really explosive, so I strongly recommend opening the bottle(s) outside in the garden as it will will overflow - a bit like Champagne or Cava.
PS The rose petals ones didn't work so well.
Elderflower Champagne Recipe
12 - 20 heads of elderflower (depending on their size, some of mine were small)
Juice and zest of two lemons
1 tablespoons of white wine vinegar
14 litres of cold water
You will also need a sterilized bucket with tight fitting lid; and glass bottles with tops.
Dissolve the sugar in a bowl of hot water. Add the lemon juice, zest and vinegar and stir well.
Pour the contents into bucket. Pour the cold water over. Leave for three days. Strain the liquid and pour into sterilized bottles.
I managed to fill 24 x 550ml sized bottles, and only because I had some, I added a few rose petals to a couple of bottles before putting the tops on.
After two weeks the liquid should be sparkling and ready to drink.
We had about a glassful left over and drank it neat, very reminisce of the sweet and golden Muscat wine. I am optimistic the bottled product will be delightful, but I will share more in two weeks time.