How do I make and preserve home-made cordials?

[ionesmum]

Our garden is stuffed with lots of goodies - elder, rosehips and blackberries - and I would like to make cordials. How do I make them and make sure they don't start fermenting? Or can I freeze them? TIA!!!

We seem to have loads of elderfower trees/bushes round us. All up the lanes and across the road and in gardens - mind you we do live in the middle of nowhere. Like the sound of fried eldeflowers suedonim - definitely different!!!