If that is a UK number with this exact number of digits... (020) 851x xxxx then that is a LONDON, UK, number. You'll also need the 851x part of the number to locate which part of the city that is. A Google search for '020 851x' will show many entries and lead you to the right area.
In the UK, area code 020 (or +44 20) is London.
In the Netherlands, area code 020 (or +31 20) is Amsterdam.
Other countries have area code 020, or codes beginning with 020.
Country code +20, dialed as 00 20 from many places, is Egypt.
(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.)
UK telephone area code 020 (or +44 20 in international format) is London and a few surrounding areas. It used to be possible to narrow down the location to a particular district of London by looking at the next four digits, but with number portability, any particular 020 number could be located anywhere within the greater London 020 area.
In the UK the code 020 is a London area phone code.
If this is the UK, then (020) 8561 xxxx is in London.
In the UK, area code 020 is London.
In the UK, area code 020 is London.
UK telephone area code 020 is London.
UK area code 020 is London.
UK area code 020 is London, but there are no valid numbers beginning with 020 4, much less 020 43. Also, the area code for London is just 020, not 020x or 020xx. There are no other UK telephone area codes beginning with 020.
Bromley is covered by the area code for London, which is 020.
A UK telephone number like (020) 84xx xxxx will be in London. You need to state two more digits in order to be able to work out which part of London; eg. (020) 8484 or (020) 8411 etc.
In the UK, area code 020 is for landlines in London. 84 would be the first two digits of an eight-digit local number.
In the UK, area code 020 is London. There is no area code 0208.
In the UK, area code 020 is London. A number beginning with 020 8488 could be located anywhere in the 020 London area. It is not possible to specify the location more specifically.
020 is London. 020-3 numbers can be anywhere in London. The operator who "owns" this number is Frontier Systems. Note that the area code for London is just 020, not 0203 or 0207 or 0208.
UK telephone area code 020 serves London. You need the first four digits of the local number to have a chance at narrowing down what part of London, and even then, with number portability, any specific 020 number could be located anywhere in the greater London 020 area.
In the UK, area code 020 is London, but there are no numbers beginning with 020 2. Other countries may have similar telephone area codes.
UK telephone area code 020 is London and surrounding areas. It is not possible to narrow down the location any further with the information given. Furthermore, with number portability, any specific 020 number could be located anywhere in the greater London 020 area.
UK domestic area code 020 is London. Although you will often see references to area codes 0208, 0207, and 0203, these are incorrect; the correct area code is just 020, and the next digit is the first digit of the 8-digit local number. However, there are currently no valid numbers beginning with 020 8103.