I don't think you can put it down to a specific area as it's possible that some exchanges were only partially affected. BT have claimed only 9,000 users were affected which is obviously nonsense as Plusnet's users on-line graph shows around 25,000 of their users lost connection (they also have substantial numbers of users on IPSC).
Thanks, jelv. It makes you wonder why BT have to be so "economical with the truth" !
Wagstaff
"Time is a great teacher, but unfortunately it kills all its pupils"