New gardening programme - sounds right up my street!

Must remember to catch this next week! Looks fab and scarily exactly what I'm trying to do. Can the BBC read my mind...

The Edible Garden - BBC 2, Wednesday, 8pm

Elderflower cordial recipes?

I have just fallen in love with some elderflower cordial I purchased from IKEA. My parents have an elderflower tree so I'm sure I could knock a batch up fairly easily. I've found loads of recipes but has anyone tried to make their own before? When is the best time to harvest the flower heads?