EDIT: I sort of grew up with ring mains, and only ever thought of the advantage: I've just read the wiki article in my link, and I can see that, if one can afford lots of cable, a ring is not such a good idea.
Capt Rajesh, Doors, and Suri - please reread my post no. 16 above. I had posted incorrect information that has now been corrected. I have to thank Cranky for pointing out my error.