You got a point about the whistling but generally I like the song. Quite a lot. I don't dig the Churchill theme much but reading the lyrics without context I like them a lot, except the naked part which doesn't click. The solo & guitar sound are terrific in my opinion and melody -wise it's the most closest to power ballad that they've ever written.
I'd pick Coming Home over it due to superior theme & lyrics but purely musically speaking, Darkest Hour is my best Maiden ballad.
Oh and I hate the seagulls, the length of it.