Almost every country has its own area code and number format when it comes to telephone numbers. To a foreigner, these numbers and formats seem confusing, but to a domestic, they are easy to identify. U.K. landline numbers contain at least ten digits, but it depends on the area receiving the call from this U.K. number. Someone in Europe receiving a call from a U.K. landline would see an additional area code in front of the number, and someone in the United States would see yet another area code.
Check the U.K. landline number wherever you have it listed or on your phone's caller ID if someone called you from that number. The number will vary depending on your location. If you are in Europe, you will see +44 in front of the number, or 0044 or just 044. If you are outside of Europe, such as in the U.S. or Canada, you will see 01144.
Separate the digits of the U.K.landline number. The correct format for a U.K.landline number is +44 (xxx) xxxx-xxxx. The digits in parentheses, usually consisting of three digits such as 020 for the London area, represent the area code. All U.K. landline numbers contain eight digits, not including the area code.
Consult a recently updated list of U.K. area codes, such as from OfCom, to determine the area code of the number. Note that area codes are between three and five digits. If the number you have does not fit the above mentioned format and does not contain an accurate U.K. area code, it most likely is not a U.K. number.
Write down the number the way you would call it from your destination. Remember to use the correct area codes, such as 011 if calling from the U.S. or Canada, or +44 if calling from Europe. If calling within the U.K., you just need to dial the area code for that area, such as 020, and the eight-digit phone number unless the area code is the same. In that case just the eight digits will be enough.