"Create a recipe for cheddar and thyme scones inspired by '100 Magnificent Muffins & Scones' by Felicity Barnum-Bobb. Use these ingredients: self raising flour, salt, baking powder, butter, mature cheddar cheese, thyme, whole grain mustard, milk. Make it suitable for a savory bread/roll, afternoon tea, lunch, English-style, and vegetarian. Include metric measurements, clear step-by-step instructions, prep and cook times, yield, and helpful notes. Use metric units only."