Grease a 23 cm (9 inch) cake tin, then line the base and sides with parchment paper.
Break the biscuits up roughly, then put in a food processor and whizz until fine then pour into a bowl. Stir in the sugar then add the melted butter and mix thoroughly. Tip the crumbs into the cake tin and press into the base of the tin. Put in the fridge to set for an hour.
Preheat the oven to 170°C/150°C fan/gas 3½.
With an electric mixer beat the cream cheese and sugar until soft then add the soured cream and mix well but gently. Add the eggs a little at a time, mixing in each one until incorporated. Add the lemon zest and juice and mix well.
Pour the mixture over the biscuit base. Bake for 1 hour or until the cheesecake is a light golden colour, but still a bit wobbly in the middle. Leave to cool in the oven with the door ajar. When cool refrigerate overnight until chilled.
Just before serving remove the cheesecake from the tin then spread with the lemon curd. Decorate with lemon slices and blueberries if desired.