On Fri, 16 Nov 2007 05:21:06 +0000, James Farrar
wrote:

One of the mobile companies -- Vodafone, I think -- that displays the
area the mobile is in on some handsets' screens displays 0207 / 0208,
too.

I put that down to the silly numbering conventions:

Large cities (e.g. Birmingham) = 4 digits (0121)
Provincial towns = 5 digits (e.g. 01772)
'02' numbers (e.g. London, NI, Cardiff) = 3 digits
Mobiles = 5 digits