I know this is more expensive than the Dixon's deal, but hopefully will help someone aiming for a waterproof one.
The Crumpler Le Royale 17" W laptop bag in Black/Grey fits 17" W notebooks (including MacBook Pro) and is made from the Crumpler 'Holycow real leather' with waterproof ripstop lining. It is padded and has a very strong zip with a soft internal cover to protect your laptop from scratches. The Crumpler Le Royale features a shiny Crumpler badge.
Link to reviewhttp://www.ephotozine.com/article/Crumpler-Le-Royale-17in-Laptop-case-9658