It can be fiddly back at home cutting the stalks off, and if you don't they seem to add their horrible smell to the mix. I grab a head of flowers on the tree with one hand, slice it off the tree with scissors with the other, very close to the flowers, and drop the handful of loose flowers into a bag slung over my arm. It's quite quick, just in case it's useful to anyone else.
I always add citric acid to bring out the lemon flavour, and because it doesn't keep for very long, I freeze the syrup in yoghurt pots. Because it is syrupy it stays slightly soft, and a frozen teaspoonful in a glass of water is cooling and delicious.