There are many organisations that have interests and responsibilities for many buildings in London. Information is available on their websites. These include: National Trust; English Heritage; the Preservation of Rural England; Museum of London; Design Museum; and then there are the London Festival of Architecture; New London Architecture; and Open House.
Explain about Listed Buildings?
There are a number of professional bodies and trade associations related to the built environment located in the greater London area or having active Branches including: Association for Project Management (APM); Chartered Institute of Building (CIOB); Chartered Institute of Building Services Engineers (CIBSE); Institute of Civil Engineers (ICE); Royal Institute of British Architects (RIBA); Royal Institute of Chartered Surveyors (RICS); and other members of Construction Industry Council (CIC).