Line a small loaf tin with cling wrap, leaving some extra wrap to hang over the edges
Heat the marmalade, Ribena blackcurrant Syrup, and icing sugar (I chose to omit this since I prefer to under sweeten my desserts, but you may add it as per taste) on low heat till it melts into a thick syrup.
Remove from heat, Add the crumbled biscuits and mix well to coat the biscuits completely with the marmalade mixture. Allow to sit for 10 - 15 minutes for the marmalade mixture to soak in.
Break the chocolate up into squares. Combine with the butter and heat in a microwave for ~ 1 minute. Stir well till the chocolate is completely melted, shiny & combined with the butter.
Add the chocolate to the biscuit / marmalade mixture and stir to ensure that the biscuits are completely enrobed with in the chocolate.
Pour the mix into the lined loaf tin. Smooth the surface with an offset spatula. Cover the surface of the cake with the overhanging cling wrap and leave in the refrigerator to chill for ~ 2 hrs.
Heat the ingredients for the ganache icing (except for the sea salt and candied orange peel) in a double boiler and mix well until smooth & shiny.
Once the cake has chilled, remove the cling wrap and drizzle with the ganache. Sprinkle with the sea salt crystals and the bits of candied orange peel.