I recently tried my hand at this Lamington recipe (for the sponge base) care of Beatrix in North Melbourne and it worked very well... I would definitely consider this a fail proof sponge recipe and the Neopolitan twist was achieved by making both caramel and raspberry sauces along side the traditional chocolate sauce.
Icing Sugar 300g
80mls - 100mls Boiling Water
Combine ingredients in a bowl and mix.
To make the caramel and raspberry sauces simply omit the cocoa and add an extra 30g of icing sugar to the mix, then add a few drops of water based flavouring to taste.
Icing sugar 330g
80mls boiling water
Flavouring to taste - a few drops
If you do follow Beatrix sponge recipe the following images may be a helpful reference
cooked sponge cooling on the bench
once cooled, cut your sponge into even portions
dip sponge squares in icing/sauce mixtures then roll in coconut
leave on a tray to set and store in an air tight container till serving time