Country Code +44
Area Codes in the United Kingdom are determined largely by the density of telephones in a given area. Since the codes in use probably number in the thousands, they are too numerous to list here. Codes are changed or added regularly -- major changes were made to city codes and mobile phone codes in April 2000.
British Telecom, the country's major telecommunications provider, operates a Searchable Online Directory.
By special arrangement, calls from Northern Ireland to the Republic of Ireland
are billed at domestic rates,
while those from other locations in the UK are billed at international rates.
International City Dialing Codes