Present day:
Since the early 2000s, all telephone numbers beginning with "07" in the UK are either mobile, pager or personal 'find-me-anywhere' numbers. They are all 11 digits long.
Specifically:
Numbers beginning 070 are 'personal' numbers that the owner can redirect as required (e.g. to work, home, mobile phone depending on time of day). These can cost up to 50p/minute to call.
Numbers beginning 076 are for pagers, while numbers beginning 075, 077, 078 or 079 are mobile phones.
Historically:
Before the national renumbering carried out in 1994, 0702 would have been the area code for Southend-on-Sea in Essex. This has since been replaced with 01702.
How many digits does the number have?
If it matches (0702) XXX XXX, then that number was perhaps issued pre-1995 and today is (01702) XXX XXX -- Southend-on-Sea (SO).020 is the area code for London.
More specifically, most (but not all) UK phone numbers beginning (020) 7xxx xxxx are likely to be in Central London.
http://www.magsys.co.uk/telecom/codelook.asp features a tool that may help you confirm a more specific location.
Note that "0207" is not an area code itself; the "7" following "020" is in fact part of the eight-digit 'local' number.
Area code 01207, which was 0207 until "phONEday" in 1995, is Consett, in County Durham. Local numbers are 6 digits.
A UK number beginning with 070 (or +44 70 in international format) is a personal "follow-me" number, which can be forwarded to almost anywhere in the world.
(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.)
A UK telephone number beginning with 070xx (or +44 70xx) is a personal "follow-me" number that can be forwarded to almost anywhere in the world.
(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.)
In the UK the code 070 (or +44 70 in international format) is used for personal "follow-me" numbers, that can be forwarded to anywhere in the world.
(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.)
A UK telephone number beginning with 077 (or +44 77 in international format) is a mobile phone. Note that a number beginning with 07700 is a mobile specifically from Jersey in the Channel Islands.
(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.)
A UK telephone number beginning with 070 (international: +44 70) is a personal "follow-me" number that can be forwarded to anywhere in the world.
(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.)
In the UK, 07902 (or +44 7902) is a mobile code. Mobile numbers begin with 074 through 079.
All UK area codes begin with a 0. There is no area code 6010 in the UK, and there is no 06010 code either.
UK area code 020 is London.
There is no area code 20 in the UK
There is no 01134 code in the UK.
The country code and area code of Aberdeen, United Kingdom is 44, (0)1224.
Cambridge is in area code 01223, or +44 1223 from outside the UK.
In the UK, 0121 is the area code for Birmingham.
Until the early 1990's, area code +44 21 (or 021 within the UK) was Birmingham, which is now area code +44 121 (or 0121 within the UK). There has never been an area code +44 217 (or 0217) in the UK.
The area code "029" is assigned to the city Cardiff in Wales, UK.
Slough. There is no 0753 code in the UK.
There is no UK area code like 0491. If the number is pre-1995 then this area code is now 01491 which covers Henley-on-Thames.
UK area code 0161 is Manchester. 0161 644 is an unused prefix.