In London there are several popular location who offer Blue Badge parking, these bays allows the driver to park his or her car for free. There are few bays which only allow the driver to stay for maximum four hours, but there are some bays which allow staying for a maximum limit. You can check the locations of the Blue Badge bays in London from Blue Badge Car Parks.
There are few locations which do not offer the Blue Badge bay but they have their own parking concession. So before you use your Blue Badge permit make sure whether the location has its own parking concession or not.
Do keep in mind that the citizens of London who hold the Blue Badge permit card do not need to pay the Congestion Charges, but for that you will have to get yourself registered with the Transport for London department by simply filing a form. For further assistance you can directly visit Blue Badge London's Website.