One can occasionally find documents in the Library, produced by the British Information Services (BIS). Now defunct, at least under this name, the BIS historically maintained offices in several cities in the United States and Canada for the purpose of disseminating information about current issues which the UK Government had an active interest.
BIS offices provided a number of services to the public including a library, with an inquiry section, a collection of films, and "illustrated booklets, posters, periodicals, and information papers on various aspects of British affairs. These materials were made free of charge to anyone expressing an interest. Today, these materials offer an extraordinary view of the British perspective on topics such World War II, the British Commonwealth, Indian independence, and African Decolonisation, for example.
A great many British Information Service materials--pamphlets, information papers, periodicals, photos, and films--have been digitized and many are freely available on the Web. Links provided on this page offer a quick start. Some titles found on linked pages will have limited access, but these can be obtained through interlibrary loan if desired. You can also search for additional resources using terms such as "British Information Services"; "Ministry of Information".
HathiTrust has a large collection of digitized materials on the Internet. Many are freely available, but not all.
Review the results organized on the left of the results page, or simply scroll through the results presented.
Results returned on the Worldcat.org website are library records, which can provide needed information in order to request desired items through interlibrary loan.