I decided to make it for Christmas but I couldn't wait so made it for my birthday today (well tomorrow as I write this).
I sandwiched the cake with chocolate spread and cream and topped it with chocolate brazils and Maltesers. I had to shave a bit off the sides of the cake because it came out slightly too tall to fit the chocolate dome over. The dome was a pain as it wouldn't come out of the bowl I'd molded it in and I had the bright idea loosen it a bit with the help of a hairdryer but I ended up melting it all down! Starting again, and running out of time I lined the bowl with cling film which worked a treat but made it wrinkly so doesn't look as spectacular as I was hoping. I finished it off with a drizzle of melted white chocolate.
Here it is inside and out:
It may not look as good as I hoped but it tastes great!