Put the flour, sugar, baking powder and salt in a large bowl and rub in the butter. Toss in the oats and milk, and mix to a soft dough. If the dough is too dry, add a few more drops of liquid. (This dough can be made easily in a food processor, using the dough attachment). Cover the dough in the bowl, and set aside for half an hour at least, or upto a day.