You also can't assume that the user knows how the number should be formatted/split. When Sheffield moved from six to seven digit numbers, '2' was prepended to a

You also can't assume that the user knows how the number should be formatted/split. When Sheffield moved from six to seven digit numbers, '2' was prepended to all existing numbers, so 0114 XXX XXX became 0114 2XXX XXX. A fairly large number of people interpreted that as an area code change instead of a actual number change (see, e.g. [0]), and I still see signs giving business numbers formatted like "(01142 XXX XXX)". [0] http://www.thestar.co.uk/what-s-on/out-and-about/calling-sheffield-0114-3-1-290413 http://www.thestar.co.uk/what-s-on/out-and-about/calling-she...