This paper in PLoS One is fascinating (if heavily blogged already). Basically, BT let some researchers from MIT, Cornell, UCL, and their own R&D division have an anonymised slice through their call-detail record (CDR) pile, the database from which phone bills are calculated. The scientists filtered out all the numbers that only made or accepted calls, in order to get rid of the call centres and spammers, and drew the rest as a massive directed multi-graph network. The conclusions are fascinating; in human terms, Wales isn't a meaningful unit, and neither is England. Scotland, however, forms a well defined sub-graph.
Instead, Wales splits into three geographic tiers with very little interconnection. These regions don't respect the border at all - not surprisingly, the northern tier is completely integrated with Liverpool and Manchester and the central tier with the West Midlands. South Wales is clearly identified, with a sharply defined border along the water between it and the West Country. There's also a well-defined western border to Yorkshire, and interestingly also between the West and South Ridings but not between them and the North Riding. Essex is an extension of London, but Kent is distinct. So is Norfolk.
In fact, England isn't really identifiable on the maps: surprisingly, the administrative units that fit best to the BT data are the EU regions much hated by 'kippers. More broadly, if it's got a recognisable accent, it's a recognisable presence on the graph - although the big exception is Yorkshire. There's even a territory for people with no recognisable accent, a sort of motorway crescent to the west of London which is described as a "tech corridor" - in fact, if you were to draw all the Formula One teams' workshops on the map, they would essentially all fall within it, as would Vodafone, O2, Cable & Wireless, and 3UK's headquarters, Aldermaston, Eidos, Surrey Satellite Tech, chunks of BAE and Thales, and Electronic Arts UK, so perhaps they have a point. In the end, though, this potentially interesting zone - Ballardia? - gets lumped in with the Cameroonian central-southwest.