Blend the biscuits in a food processor until it turns into fine crumbs. Combine crumbs with melted butter. Line the bottom of a 9 inch springform with parchment paper and cover with the mixture, pressing down evenly. Put in the fridge.
Whip the cream cheese and sugar until smooth and add the whipped double cream. Mix until smooth and transfer half the mixture to another bowl.
In a food processor, blend the blueberries with icing sugar. Take about ⅓ of the blueberry mixture and add it to one half of the cheesecake mixture. Strain the rest to remove any seed or skin and set the rest aside in the fridge.
Pour the plain cheesecake mixture on the biscuit base, spread using a spatula and add the blueberry cheesecake mixture, then spread again. Place in the fridge.
Meanwhile, make the blueberry G&T jelly. Dissolve the gelatine sachet in a jug with 115ml of hot water. Stir briskly until thoroughly mixed. Add the gelatine mixture to a mixing bowl with the remaining blueberry puree, gin and tonic. Mix well and pour over the cheesecake. Refrigerate overnight and serve with a slice of lime.