Found this, might be worth a try

Rose-hip cordial
You need:
900g wild rose-hips
1.8 litres water
275g sugar for every 600ml juice
squeeze of lemon juice to taste.
What to do:
Boil the water in a large saucepan and put in rose-hip 'mash' and simmer for 15 minutes.
Strain the juice through a jelly bag or muslin. Measure the juice and add the appropriate amount of sugar and lemon juice.
Heat together until the sugar is dissolved.
Fill up clean warmed bottling jars and stand them in a shallow tray in an oven at 150 degrees.
Bring to simmering point and allow a further 20 - 30 minutes more cooking.
Leave to cool and store in a dark place.