I finally tried this and discovered it's not difficult at all! In fact I used store bought trifle sponges so the cake was ready in no time at all.
One each vanilla and chocolate sponges, 250ml fresh cream (beaten till stiff), jam, flake
It's best that you look at my photos attached as it will make it easier to understand. Cut each sponge in half so that you have two vailla and two chocolate discs. Then cut out the innermost circle first and then the next circle. You should have 3 pieces of cake per disc. Then place alternate colours in each disc. Use the jam around the edges of the discs before placing it in the main disc. This will allow it to stick together so that it does not fall apart when you slice the cake. Then place a completed disc, with the vanilla on the outside, on your serving plate. Cover with jam and a layer of fresh cream. Then palce a disc, with the chocolate on the outside, over the bottom disc. Spread with jam and fresh cream. Then do the same with the last two layers. Spread the top with jam and cream and decorate with the flake. Enjoy!