Hi DiS, being the cool, fashionable people you are I'd like to pick your collective brain about what new bag I should get. I've had one of those Fred Perry shoulder bags (http://www.kinowear.com/images/fredp_mess.jpg) for years now and it's falling to pieces - Looked cool in college, was absolutely ubiquitous at university and so became less so, and now it's time is finally over and needs an upgrade.

I'm a teacher so it needs to have room for afew book, pencil case etc., and a packed lunch. Any suggestions?