If that is part of a UK number, then it will be a London number (London's area code is 020).
It is not possible to give a more specific location for numbers in the range (020) 3189 xxx.
Area code 020 is London. A London number beginning with 020 8248 is most likely to be served by Virgin Media Ltd., and could be anywhere in the Greater London 020 area. Furthermore, with number portability, the number may be served by another carrier.
UK telephone area code 020 (or +44 20 in international format) is London. The 020 3129 prefix is a "virtual" prefix, so numbers in that prefix could be located anywhere in the greater London 020 area. Furthermore, with number portability, any specific 020 number could be located anywhere in the London area, served by any local telephone company.
(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 area code 020 is London. A number beginning with 020 3298 could be anywhere in the greater London 020 area.
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.
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.
Bromley is covered by the area code for London, which is 020.
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.
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.
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.