E Barnacle, m'lad
Hope this link works.... it was what I meant to post here earlier to help Abby 'get' something she said she couldn't grasp.
http://ww2010.atmos.uiuc.edu/guides/mtr/hurr/gifs/mvmt1.gif

It shows (roughly) the trades etc. The way I understand it, behind you for some parts of the 'trip', in your face for others...
in both directions, to and from UK to Port Jackson/Botany - hence need for some 'tacking'.
Mebbe it's me that's just not getting something?
I had read all the posts...
I certainly didn't mean to make any hackles rise.
Merely tried to 'add to' existing posts.
Apologies if any offence caused...- D