Heat the butter and golden syrup in a saucepan, stir in the biscuit crumbs and mix well. Tip into a greased 23 cm (9 inch) springform tin, and press over the base of the tin with the end of a rolling pin. Chill while making the filling.
Whip the cream in a large bowl until it forms soft swirls. Add the lime rind and condensed milk and gently fold together, then gradually mix in the lime juice. Pour over the biscuit base and freeze for 4 hours or overnight.
Loosen the edge of the pudding from the tin with a round-bladed knife, remove the sides, then slide off the base on to a serving plate. Spoon the seeds from the passion fruits over the top, then scatter with the blueberries. Allow to soften for 30 minutes before cutting into slices to serve.