I hope eventually to include on this site more details of at least some of the following:
The original (1958) charging scheme - 640 charging groups, c. 800 numbering groups
The Numbering Group Codes (only in Northern Ireland) covering more than one Charging Group
Core and Ring Numbering Schemes (e.g. Cardiff core = OCA2, ring = 0GG7)
Charging Groups covered by more than one Numbering Group
Alphanumeric Numbering Group Codes (e.g. 0CB3 = Cambridge) and
Dialling using Exchange Names in Director Areas
(Roger Haworth's site has some information on Letters for digits in UK telephone numbers)
Progress on the Introduction of Subscriber Trunk Dialling (STD) from 1960
Renumbering of the 0Oxx Numbering Groups (e.g. 0OX2 Oxford to 0865)
Reuse of 00xx codes for various purposes.
Miscellaneous Numbering Group changes (e.g. Market Harborough from 0645 to 0858)
Exchanges that moved from one charging group to another (there were very few!)
Exchanges which changed name, other than as a result of incorporation into a lnked-numbering scheme (again, there were very few!)
Relief (mobile) telephone exchanges and their names. Usually green (later blue) vans parked in the exchange yard. Often named thematically - names incorporating "green" were popular, names with a "park" suffix were common in South Wales, and Bedford area named them after birds.
The change to purely numeric Numbering Group Codes and the introduction of All-Figure Numbers in Director areas
The splitting up of some of the Numbering Group Codes in Northern Ireland covering more than one Charging Group
Amalgamation of Charging Groups to release Numbering Group codes
Reuse of Numbering Group codes for Non-Geographic purposes.