Today the children and I screeched to a halt along the Sefton Road, and excitedly picked a whole box of elderflower heads. It's probably best not to get them from, the road, but they are the only ones I have access to. You need to pick them in full bloom when the whole head of flowers are white. Discard any that have unopened flowers on.
To identify Elderflowers see this link http://elderberries.ning.com/
I have just put the first batch of champagne on to brew, and am about to make some cordial. Both these recipes are tried and true, I have made them for several years now after being inspired by Hugh Fearnley-Whittingsall (or as the Brits say "Who Fearlessly-Eatsitall" :P
Bring 1.5l of water to the boil and dissolve in 1.5kg sugar. Add about 30 heads of elderflower in full bloom, 3 lemons, first the rind which you have grated off, and then slice the lemons and chuck them in, and 75g Citric Acid.
Let cool and steep for 24 hrs before straining and bottling. Will keep for months.