I think the reason it went well with DS was because I moved the time of the milk from BT to dinner so by BT he wasn't really interested in the bottle that I did offer.
I also think this is why he didn't want to move to a sippy for the morning milk but I 'think' if I move that time too he might be more agreeable (eg if I offer breakfast first then the milk from a sippy or straw cup/carton with first snack it might break the morning bottle habit like it did the BT one).