I've drawn up a guide to setting up the Pi as a wireless internet router using the kit mentioned in the title - not as simple as I thought it would be thanks to Huawei devices having 2 modes (modem and storage) and the Edimax adapter being incompatible with the off the shelf version of hostapd (the thing that deals with authentication on the wireless network). Hopefully I encountered and overcame enough problems for this to be of use to someone 
Anyway here is the link: http://bigcowpi.blogspot.com/2013/03/raspberry-pi-as-3g-huawei-e303-wireless.html
This is the first time I've done the whole blog thing, so any feedback would be appreciated.