Mix together oats and buttermilk in a bowl. Cover and refrigerate overnight.
Sift together flour, sugar, baking powder, bicarb, cinnamon and salt in a large bowl. Cover and let sit at room temperature overnight so that it's ready and waiting in the morning.
The next morning: Make a well in the centre of the flour mixture and pour in oat mixture, followed by the eggs, butter and raisins. Stir until just moistened. Allow batter to rest 10 to 20 minutes before cooking. If batter is too thick, add buttermilk, 1 tablespoon at a time, until batter reaches the desired consistency.
Heat a lightly oiled, large frying pan over medium heat. Pour 60ml batter onto the hot griddle for each cake. Cook pancakes until bubbles appear on top, flip and cook until lightly browned on bottom.