Pritanoi Reborn is a partial modification for Rome - Total war version 1.5, made by myself, which completely overhauls the Britons faction and the map of the British Isles, and makes several other changes to other barbarian units. Instructions are included in the download. Screenshots and information can be found in the thread in the modding section: http://rtw.heavengames.com/cgi-bin/forums/display.cgi?action=ct&f=9,8837,0,all
Any and all feedback appreciated, particularly errors. This is only the initial release, there will no doubt be minor adjustments and bug fixes in the future still to come.