Good luck, OP! Having looked at that BBC guide it seems to me that what you want to end up with is four sponges of identical size, and if you want to you can make two of one type and two of another. The recipe gives you two malt-flavoured and two chocolate-flavoured, but you could do other flavours. Contrasting sponges would make it look very effective when cut into as well as providing flavour contrasts.
I like to go through a recipe before I try it to be confident I know all the different elements and have allowed enough time. That recipe looks clear and makes sense to me, so I'm posting this as a reminder to myself to come back to it next time I need a celebration cake (goodness knows when that will be, but we have to have hope!).
Once you've made your cakes you put one on a stand, board or plate and spread some icing, buttercream or jam on it. Here again, you don't have to follow the recipe exactly. Just pick something you know you'll enjoy eating and that works with the flavours and colours of the sponge. Put a contrasting sponge on top, repeat. Put the other sponge of the first flavour on, repeat. Put the final sponge on.
Now spread a thin layer of icing/ganache all over the sides of the stack of cakes (as explained in recipe this is the crumb coat and the idea is that any loose crumbs from the cakes will come off at this stage and by the time you apply the final icing/ganache you can be confident there won't be any more loose crumbs).
Put in fridge to firm up. Then remove and spread remaining icing/ganache all over top and sides smoothly and thickly.
Chill again, make drizzle, follow instructions carefully to be sure it's the right consistency to make a drizzle, put on top of cake and let it drizzle over sides.
While still soft, put on some decorations, whatever you fancy.