It is pretty easy to find WiFi internet access sin London. However not so easy to find it for free. You can find internet access on offer at many cafe’s and coffee shops but most of the time you have to pay to use the WiFi. However McDonalds, KFC, etc all offer free WiFi in many of their restaurants.

You can download many mobile phone apps for Apple iPhones and Google Android Phones which help you to find free WiFi as you travel.

FON – Free WiFi Access
https://corp.fon.com/en
FON is a scheme which aims to help spread the availability of free WiFi access throughout the world. At the time of writing they have over 12 million wifi hot spots around the world.
Although the scheme is very popular in cities such as Madrid it is still relatively little known in the UK and there are certainly not enough members actively using it in London for it to be a consistent way to get a WiFi connection throughout London. Having said that British Telecom became partners with FON some time ago and you will now see the BTFON WiFi signal in many more places then you used to.
Fon members share a bit of their home WiFi, and in turn get free access at millions of other Fon hotspots worldwide.