The question of acknowledgment has been one that has been lurking in the back of my mind. Vaughan Williams was composing mainly from 1910 to 1957 so at that point I would have thought that all of his music was under copyright, but even taking that into account the orchestral performance itself would have had copyright protection as well, so permission would have had to have been sought to use it... unless it really was a new commission at the time.
Lazypoker's point about
Questions doesn't really arise as Mannfred Mann would have just been using the melody and as Schubert died in 1828, copyright issues wouldn't have arisen. I would have hoped that he would have acknowledged its use out of politeness, though.
I'm amused at the thought of composers turning in their graves infuriated at the thought of missing out on royalties. Think Beethoven over the
Saturday Night Fever soundtrack, or Saint Saëns over the desecration of his
Organ Symphony (one of my faves) by
If I had words (which is not)