Am using packet mix for Delia's Christmas cake mix. Cake is ready to go in the oven but just realised you need baking parchment to go around the outside of the tin and baking parchment to cover the cake. Can I use greaseproof paper to cover the cake and do I really need to put something on the outside of the tin? Don't have baking parchment to do this - could I use greaseproof paper for that as well if really needed? TIA