I have been formula feeding my ds since he was 3 months with Aptamil 1 + Aptamil comfort. I am now looking to go onto the next type of milk as he soon turns 6 months. My trouble is I would love to use one of the organic brands, but love the convenience of the aptamil ready made cartons. Can you mix types of milk? Does anyone have experience of the organic brands, if so how did you find them/ can you recommend one brand above another?