Heat the oven to 190°C (170°C fan). Roll the pastry out on a floured surface until it is about the thickness of a pound coin and line a 20 cm round or square tin, letting the excess hang over the edges.
Line the pastry with baking paper and fill with baking beans, dried rice or a scrunched up sheet of foil. Blind bake for 15 minutes, then remove the paper and beans and bake for another 5 minutes until the base looks dry.
While the pastry bakes, fry the bacon bits in a dry pan for 5 minutes until the edges crisp. There is usually enough fat in them that you will not need oil.
Beat the eggs and milk together in a jug, stir in the grated cheese and plenty of black pepper, then mix in the bacon.
Sit the tin on a baking sheet, pour the egg mixture into the pastry case and carefully slide it into the oven. Bake for 25 to 30 minutes until the filling is set with a slight wobble in the middle and the top is golden.
Let the quiche cool in the tin for 10 minutes, then trim the overhanging pastry with a sharp knife and slice. Eat warm or let it cool completely and keep it in the fridge for lunchboxes.