Dear Mr. Rawles,
I thought you might find these two articles on microgrid technology to be of interest. They raise the possibility that a well-organized community might be able to continue functioning even after a general grid failure:
Also, major manufacturers are gearing up to produce a new generation of deep-cycle batteries that can be recharged thousands of times, further facilitating the creation of off-grid communities.
Thanks for your great site. Regards, - Dave T.