I intend to have a go at this syrup over the weekend.
grated rind and juice of 1 kg/2lb (about 8 lemons)
grated rind and juice of 2 oranges
1kg/2lb granulated sugar
1.2 litres/2 pints of water
2 x 15ml/ 2 tablespoons of citric acid
Put the grated rinds into a large saucepan then add the sugar and water and bring to the boil slowly stirring to dissolve the sugar.
Pour the squeezed fruit juices into a large heatproof bowl or jug then pour on the boiling syrup; then stir in the citric acid. Leave to cool. Strain and then pour into prepared sterilised bottles leaving about 2.5cm/1/2 inch to 1 inch headspace in the top of the bottle. The bottles then can be processed using the heat process or by Campden solution. I prefer to hot water process the bottles rather than adding anything further to the product. Please see my post here as to how to go about it. http://tarragonnthyme.blogspot.com/2012/01/sterilising-bottles-or-jars-by-heat.html
Substitute oranges, limes or grapefruit for the lemons and use lemons instead of the oranges