Preheat the oven to 375°F (190°C or 170° for a fan oven).
Line a 12 cup muffin pan with paper baking cups.
In a large bowl, mix together the flour, oats, sugar, baking powder, baking soda, salt, cinnamon and nutmeg.
In a medium bowl, mix together the egg, buttermilk, vanilla and oil.
Pour the wet ingredients into the dry ingredients and stir just until mixed.
Gently stir in the raisins or sultanas.
Scoop the batter into muffin cups - I use a quick release ice cream scoop or a ⅓ cup measure to do this.
Bake for 15 to 20 minutes or until a skewer inserted into the centre of a muffin comes out clean.
Cool in the tray for 5 minutes before transferring to a wire rack.
Muffins taste best slightly warm but they reheat well the next day.