I made cordial! It never really occurred to me to try before. I didn't have a proper recipe, just some basic instructions:
Take equal parts lemon juice and sugar, combine in a pot and stir over low heat until sugar is dissolved. Thats it : )
You only need a small amount, added to cold water, to make a really refreshing drink. It's delicious, and even better with tonic water.
After I had juiced all my lemons, I threw out the skins - not realising they were all I needed to make my own preserved lemons. Oh well. Next time.