Beat the butter, sugar and vanilla together using an electric mixer, until pale and creamy. Add the eggs, one at a time, beating between each addition until combine. Sift in the wholemeal and plain flour, bicarbonate of soda, baking powder and cinnamon salt. Add the bran, milk and lemon juice and stir to roughly combine. Add the blueberries and stir until just combined. Do not over mix. Spoon the mixture into the prepared muffin holes, distributing the blueberries evenly.