Heat the oven to 180C/160C fan/gas 4. Butter and line a 30 x 15cm rectangle tin with baking parchment. Melt the butter, sugar and honey in a pan over a medium heat, stirring frequently until the butter has melted and the mixture is smooth.
Put the oats in a mixing bowl, then pour over the butter and honey mixture. Stir until all the oats are coated. Tip into the prepared tin, and use a spatula or the back of a spoon to evenly spread out the mixture. Cook for 10-15 mins until lightly golden. Leave to cool in the tin, then remove before cutting into squares.