In a bowl mix the egg yolks with corn flour and water until smooth. Heat the single cream in a saucepan. Do not allow to boil. Pour it to the egg yolk mixture, stirring all the time. Transfer the mixture to the pan and place it over a very low heat. Stir the mixture continuously until it gets thickens and pour into a bowl.
Puree the mango slices in a blender until smooth and sieve. Mix it with the custard and stir in the lime juice. Whip the double (heavy) cream until soft peaks form. Fold into the mango mixture until thoroughly combined.
Transfer the mixture to a freezer proof container. Cover and freeze until half-frozen and still mushy in the centre. Turn the mixture into a bowl and mash well with a fork until smooth. Return to the container, cover and freeze again until firm. Keep the container in the main compartment of the refrigerator for about 30 minutes before serving to allow the ice-cream to soften slightly.