I did finish my cake a week ago on Monday in time for when the family came to visit. Here is the finished item.
I did a chocolate butter cream filing and finished the top with melted chocolate and sugar butterflies as you can see. Not necessarily the most artistic finish but the family did seem to enjoy eating it even if the sponges were a little overcooked.
I will need to get smaller cake tins if I ever use this method again but it was interesting to try...
Now back to knitting as I know what I'm doing most of the time!