Cut the melons in half and scoop out the flesh with a melon bailer, or cut into cubes.
Place in a bowl.
Reserve the shells.
Skin the grapes, halve and remove any pips.
Add the grapes to the bowl and pour over the wine, then add the chopped ginger and sugar to taste.
Mix well, cover and chill for 2 hours.
Spoon the mixture into the melon shells and serve immediately.