Although many of these have have since changed, the detail provided on the large city codes can be useful. An explanation which includes information about charge groups and how they work. BT Archives preserves the documentary heritage of BT and its predecessors, including paper copies of phone books back to 1880, available for reference. Electronic Yellow Pages are, respectively, the UK White and Yellow pages phone directories. It is very expensive, so it is typically only bought by those who intend to make a high number of searches.
Registration is necessary, but free.
There are other CDs around, sometimes compiled from dubious sources. The information they contain can be hugely inaccurate, out of date and incomplete. All rights reserved.