Thanks for the reply!
a) Thanks. I must have skipped over that in the documentation.
b) Maybe it was a problem with where I tried to insert the Gallery. I tried putting it in the homepage so I had assumed the gallery itself would take the full width (around 1000px)
c) This was actually for http://syhds.wordpress.com/ (ignore the other blog in the original post, didn't realise WP posted that info). I'm using a custom theme.
d) Yes I realise PHP (either wordpress and/or the template specifically) are somehow setting the width via ?w=462 I'm just not completely sure why it's not taking up the full width (maybe some to do with the type of template I've chosen for that particular page?).
Anyway in Lieu of finding a solution I've hacked up some CSS to insert larger versions of the images, and hack away some of the borders etc to get a full width carousel. It's works good enough, though I'm not proud of my CSS hacks.
If you have suggestions on how to achieve the same thing that I've done, but properly through WP I'd love to hear them!