Trim about 0.5cm/¼in from the edges of the round sponge cake so that you can stand the sponge fingers, sugar-side out, sandwiched together with the raspberry jam around the edge of a 20-23cm/8-9in diameter loose bottomed tin leaving no gaps. Push the sponge fingers down so that they touch the base of the tin.
In a large mixing bowl or food mixer, whisk the evaporated milk and lemon zest until thick and creamy and doubled in volume. Stir in the lemon juice, soured cream and caster sugar.
In a separate bowl, whip the double cream to the same consistency as the evaporated milk mixture.
Gently fold the whipped cream into the evaporated milk mixture and pour into the tin. Place in the freezer until set, preferably overnight.
Take the pudding out of the freezer 1-2 hours before required. Remove the pudding from the tin before it defrosts as it is more stable when frozen then place on serving plate.
To serve, arrange the peach halves and raspberries on top of the pudding and sift over the icing sugar.