Thanks Snorr. I just noticed that just about anyone can get Knighted today, even Rudy Giuliani.

Note that Chaplin was knighted as late as 1975, approaching 86, two years before his passing; a knighthood had been suggested as early as in the 1930s, but was then turned down, reportedly due to Chaplin's not fighting at the battle-fields during WWI (his Liberty Bounds tour apparently didn't count). In the 1950's, a knighthood was suggested again, but turned down due to Chaplin's recent troubles in the U.S. (Source: "Chaplin and American Culture, Charles J. Maland, among other books)
As to whether Chaplin did something to honor England; that depends on what one considers "honorable service" to a country. The understanding of such terms has been much broadened in later decades, also in royal circles. In this case, it was Chaplin's immeasurable contributions to the film medium as well as all the laughter he'd given a whole world, including England, for generations that was being acknowledged.