Hiya

My husband, DD and I travelled Sydney to Birmingham (and return!) when our DD was 11weeks old.

HAB definitely a good idea, but some airports may make you take your baby out of it to pass through security, so just be aware of this. I was wearing DD in an ergo and because I was wearing a hoodie underneath they told me I could walk through wearing DD, but needed to take the hoodie off! Not possible unfortunately without disturbing DD (who was asleep at the time!).

Other things I took were:
a couple of cloth nappies for burping / spews etc
plenty of breast pads for me (massive leaking issues)
2x wraps for DD (I actually took her woombie which was heaps easier than wrapping esp on the plane)
Infacol (DD had big wind issues)
Baby panadol (didn't need it though)
Blanket for the bassinette (they provide one, but wanted DD to have something familiar)
Favourite soft toy (again just for something familiar)
Nappy wallet (so that everything was all together to simply take to toilet for nappy changes)

Other tips are just to make sure you confirm with the airline that you've got a bassinette seat, also confirm that you're on the aisle the whole way through (part of our trip back we weren't on the aisle seat and it was a real pain). Also try to avoid your bubs getting overstimulated at the airport before you leave. This happened to us and DD took a bit to get settled initially.

Definitely make the effort to get breastfeeding established as it makes things heaps easier, and just be aware that when you're BF on the plane you don't have much elbow room - took me a couple of feeds to get used to this at the time. To avoid ear pain, feed on take off and landing if possible.

DD travelled really well actually overall, she fed on each take off and most of the landings she was actually asleep for. I think the hardest thing was initially when we left Sydney and she was so overstimulated. I did get thrown up on twice though and DH got pooed on so changes for you and DH are a must, DD also went through 3 changes of clothes on the flight over.

Good luck!