Preheat oven to 180 degrees C. Grease and flour a 20x30cm cake pan. In a medium bowl, mix flour, oats, bicarb soda and salt together and set aside.
In a large bowl, cream butter and sugar until light and fluffy. Add eggs one at a time, mixing well with each addition. Mix in buttermilk, bananas and vanilla. Add flour mixture and mix well. Finally, fold in the nuts, coconut and 1 cup of the chocolate chips.
Pour batter into pan. Sprinkle top with remaining 1 cup of chocolate chips. Bake for 30 to 35 minutes, or until a toothpick inserted into the cake comes out clean.