If you need to People search in London there are many ways to do so. The main methods of finding a person in London would be the same as finding someone in any other part of the UK or beyond. Big cities are no different from rural locations in the sense that some people will be on the voters roll and some won’t. I guess the advantage of trying to find someone in Norfolk for example as opposed to finding a person in London is that in a more rural location people tend to know each other a little bit better so if you are looking for a lost friend in the countryside and you phone around you will most likely find someone who knows the person, where as in London there are more people and consequently they do not have as much contact with each other. So if you are looking for someone in a rural location such Norfolk, Suffolk, Cumbria etc then you would be best serviced getting on the telephone and contacting locate people to see if they know the person you are looking for, if you have the persons old address try some of their neighbours or people with the same surname in the area.
If you need to People Search in London it may be better to get straight on to tracing them using something like the electoral roll or even Facebook. Facebook is a great way to find people in London and other big cities as you can search by their full name and sometimes it can give you their current location, it is also free to use. If you are doing any kind of People Search it is worth looking for them on Facebook.
Finding people for free in any area is good fun and there is lots more you can do, have a look around the rest of this website
Good luck with your People search in London.