What is the telephone area code for Greenford Middlesex England?

Most of Enfield is in area code 020 (+ 8 more digits) with the rest of greater London. However, the northern edge of Enfield is in area code 01992 (+ 6 more digits) with Lea Valley.

In international format, replace the leading 0 of the UK domestic area code with telephone country code +44, as in +44 20 or +44 1992.

(The plus sign means "insert your international access prefix here." From a GSM mobile phone, you can enter the number in full international format, starting with the plus sign. The most common prefix is 00, but North America (USA, Canada, etc.) uses 011, Japan uses 010, Australia uses 0011, and many other countries use different prefixes.)