Lightly oil a baking sheet with spray oil. Sift the flour and salt into a bowl. Add the butter and rub in with the fingertips until the mixture resembles fine breadcrumbs. Stir in the Cheddar and rosemary. Make a well in the centre, add the milk and measurement water and gradually work into the flour mixture to form a soft dough.
Turn the dough out on a lightly floured work surface and knead gently into a smooth ball. Transfer the dough to the prepared baking sheet and flatten slightly to form an 18 cm (7 inch) round. Using a sharp knife, score the surface into 8 wedges. Bake in a preheated oven, 200°C (400°F), Gas Mark 6, for about 30 minutes until risen and the loaf sounds hollow when tapped underneath. Transfer to a wire rack and leave to cool completely.