Pip's just found her cordial recipe if it's of any interest.

10 large flower heads
3 lemons (sliced)
2 1/2 (Imperial!!! ;-)) pints boiling water
3 ounces citric acid
3 lbs sugar

Dissolve sugar in boiling water and add other ingredients
Cover and leave in a cool place for 5 days
Stir once a day
Strain into bottles.

It winds up as something you dilute to taste.