UK Area Code Finder
Quick and easy telephone dialling code information
In the UK, an 0203 number is a normal landline phone number within the London (020) area code.
Any UK number beginning with 020 is a London number. The '020' area code at the beginning is optional if you're dialling from one London 020 landline phone to another.
There is no 0203 area code. London has a single city-wide area code of 020, used with eight-digit local numbers.
The correct way to write a number beginning '0203' is