I think that I must highlight some examples of film music by English composers. William Walton's score for Olivier's Henry V is wonderful - the opening sequence takes us into Elizabethan London and joins the groundlings in the Globe theatre. Walton's music complements the images perfectly. And his later use of three Auvergnat songs to underscore the French court is so appropriate.
Ralph Vaughan Williams also wrote film scores. He adapted the music he wrote for Scott of the Antarctic into his Sinfonia Antarctica. Apparently, he produced rather too much music for one scene. Instead of asking VW to modify it, Charles Frend reshot the scene so that the music would not be changed.
Who can forget Malcolm Arnold's music for The Bridge on the River Kwai? He turned Colonel Bogey into a national treasure.
Contrary to popular opinion, Eric Coates (another Nottingham man, Trent) did not write his march specifically for The Dam Busters. He was asked to score the film but declined - he did not like the idea of writing film scores. Apparently, he picked up a march he had recently written - an exercise in writing Elgar-style marches - handed it to the filmmakers and said something to the effect of "You can use this if you like." Leighton Lucas used the march as the basis for his score.
But ... was ever a single piece of music more appropriate for its adopted subject?
.........
Admittedly not an English composer, but at least a half-English singer - Audrey Hepburn and Moon River.