I guess if you entered a competition for home made mince pies and they found out that you used bought pastry and mincemeat, you would be cheating. A bit like in pubs when they advertise their "home made" pies that were home made somewhere else and not in their kitchen.
I think I've left it late to raise my own cow and slaughter it for the suet, grow my own wheat and mill it for the flour and candy orange peel although I could probably grate the nutmeg and grind the cinnamon if I'm allowed to buy it from the shop.
I'll settle for adding brandy to the jar of mincemeat, cutting the pastry in to Christmas trees for the lids and dusting them with icing sugar.