To make the topping, mix together 1/2 cup sugar, 1/3 cup flour, and 1/4 cup butter, and 1 1/2 teaspoons cinnamon, mix with a fork, and sprinkle over the muffins before baking. Preheat the oven to 400F, 200?c, Gasmark 6; grease the muffin cups or line with muffin liners. Combine 11/2 cups flour, 3/4 cup sugar, salt and baking powder, place the vegetable oil into a 1 cup measuring cup; add the egg and enough milk to fill the cup. Mix this with flour mixture fold in blueberries fill the muffin cups right to the top, and sprinkle with crumb topping mixture. Bake for 20 to 25 minutes in the preheated oven, or until done.