Spread the sponge cakes with the jam, then roughly crumble them into the bottom of the glass serving dish. Sprinkle over the sherry or orange juice, and leave for half an hour. Mixed the drained tinned fruit into the jelly, and put on top of the sponge cake layer. Leave until firm enough to take next layer. Spread the custard on top. Leave until firm enough to take next layer. Whip the cream and add sugar to taste, then spread or pipe on top of the custard. Trifles are traditionally decorated with rosettes of cream piped around the edge, together with pieces of angelica, those diamond shaped jellies, flaked allmonds and/or glace cherries. Refrigerate until ready to serve. Note: Use a large glass serving dish to show off the layers.