Combine the fine biscuit crumbs with the melted butter until you have the consistency of wet sand. Use this mixture to line the base of a 7 inch square springform cake tin. Transfer to the fridge to chill.
Meanwhile, soften the gelatine in the lemon juice and a little water if necessary, for 5 minutes. Heat the mixture in a small saucepan over a low heat until the gelatine has dissolved. Beat together the low-fat soft cheese and the sugar in a large mixing bowl using an electric hand-held whisk for 2 minutes.
Add the low-fat Greek yogurt and the gelatin mixture, and mix again until smooth. Finally, add the peppermint flavouring and the lemon zest and beat well. Pour onto the biscuit base and tap gently on the side to release any trapped air bubbles. Transfer to the fridge and chill for 2-3 hours until set.
When ready to serve, remove from the springform tin and cut into square portions. Cut in half again and arrange serving plates. Warm together the lemon curd and lemon juice in a small saucepan set over a medium heat until smooth and of sauce-like consistency. Let the sauce cool a little before spooning over the cheesecake. Serve immediately.