What is the zip code for Oxford England?

The telephone code for London is (020). You may see references to 0207 or 0208, these are erroneous, London became one area under a single code in 2000.

Local numbers in London have eight digits and currently begin 7, 8 or 3. You cannot rely on these to accurately define their geographical location within London. You need the next FOUR digits for that e.g. (020) 7545 XXXX, and even then some numbers may be outside their prescribed zones.

If you're dialling internationally the code for the UK is +44 and you need to omit the initial '0' from the area code eg. +44 20 xxxx xxxx.

(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.)