Elderflower and rose petal cordial

I love the elderflower cordial, and was wondering if it is difficult to make your own. We have an elderflower bush in the garden, but it is pretty young, and doesn't sport more than 3 heads of blossom this year, so I let it be. While returning from my older son's school, I noticed heaps and heaps of the white lace, and decided to do a bit of foraging. And as the roses in my garden have gone amok this year, I thought I'd make an Elderflower and Rose Petal Cordial, to combine the two quintessentially English favours.

Elderflower and Rose Petal Cordial
Ingredients:

15 heads of elderflower              
1kg granulated sugar     
1litre water
zest of 1 unwaxed lemon, cut into strips
1 lemon, sliced
20+ mixed roses

I went for the mix of roses, as I wanted for the cordial to turn pink. But I suppose the pure white roses would produce a lovely colourless cordial.
Pick the flowers, divide the rose petals and shake the elderflowers to get rid of any tiny bugs. Place in a big bowl and pour the cold water over them. Drain the water.
Place the sugar into a pan with the water, bring up to the boil, keep stirring until the sugar dissolved completely.
Using a paring knife, peel off the lemon zest in strips, add to the sugar.
Slice the lemon and add to the pan with the sugar.
Add the rose petals and elderflower heads to the sugar syrup, bring to the boil and cook for about 5 minutes.

Leave in the pan overnight under the lid. The next day strain the cordial and pour into the glass bottle.

To serve, dilute the cordial with sparkling or still water and add a slice of lemon.

I have strained the cordial into the bottles, but also left some rose petals in (the elderflower heads were discarded) for a couple of small jars. I just like to add a couple of teaspoons of rose petals in sugar syrup to my tea. It is so fragrant and flavourful. And very pretty too. I can imagine it would go nicely with champagne.
It was dead easy and cost me almost nothing (I only bought the sugar).