Place all of the ingredients in a large bowl and blend for several minutes until thoroughly combined. It doesn't matter if some of the berries are left whole.
Transfer the mixture to a freezer-proof container and freeze for 30 minutes.
Remove from freezer and mix thoroughly with a fork. Return to freezer.
Repeat process every 30 minutes a further 2 or 3 times - until the mixture is creamy and resembles icecream.
Remove from freezer 10 minutes before ready to serve.