Combine the cordial and cold water in a measuring jug. Put a few pieces of mixed fruit at the bottom of each lolly mould, then fill each with the liquid so they're a third full. Leave to freeze for around 2 hours until completely frozen. Put the remaining liquid and fruit in the fridge until required.
Remove the lolly moulds from the freezer and add a few more pieces of mixed fruit, then top up with liquid until the moulds are just over half full. Return to the freezer and freeze for a further 1 hour, until semi-frozen. Then add the last of the fruit and the remaining cordial, and insert the lolly sticks. Leave to set for at least 4 hours, preferably overnight.
To remove, take the lollies out of the freezer and leave for just under a minute to loosen.