01 and 02 geographic numbers are traditionally delivered over analog and ISDN lines. However, today’s networks allow these numbers to be delivered by a wide number of services including cloud based IVR’s, SIP Trunks and Hosted Telephony. This allows you to have a local presence in a specific town or city without having an office there.
0203 and 0207 London numbers are very popular with businesses that are actually based outside of Central London and even overseas, since they give the impression that they do business from a major UK city. London numbers also allow smaller businesses to have a presence within the capital without having an office in London. You can divert calls to your 0203 or 0207 London number to a land-line or mobile allowing you to attend meetings and take calls as normal.