Seeking information: Letters to British newspapers and foreign news subsidies

Hello. I am currently working on my PhD at the School of Oriental and African Studies (London). One of my chapters looks at how Augustus Charles Hobart-Hampden (Hobart Pasha), and Henry Felix Woods (Woods Pasha), supported the Ottoman Government through letters in the British papers and articles in periodicals. The majority of these items were published between 1876-1900. Does anyone know of any books/articles that look at the phenomenon of writing letters to the press, e.g. was it a particularly British thing to do, did it increase over the 19th century, how does the British example compare to France, Germany, the Ottoman Empire, etc.

On a separate but related subject, the Ottoman Government used subsidies to persuade papers to publish positive articles. Can anyone recommend any books which deal with subsidies to papers from government and particularly foreign governments in Britain.

Many thanks.

Yusuf Osman, SOAS London