Paul, you have noticed that Metallica's version also contains the Holst intro, haven't you? I mean, it's the first time I heard their version and I was all ready to say "Oh yeah, but with the Mars intro it's crap", and yet they use it. But you hate DH's use of it? Huh?
That song encapsulates more or less what DH were, or could have been. They were travelling in a prog rock/metal direction on that album but then sadly overdid it with the next one, and then just went off into the Twilight Zone totally. But as US says, Metallica don't finesse the song the way it needs to be. I mean, listen to it: you have the big Holst intro (boo to you for hating it; I think it sets the scene perfectly plus I love everything about The Planets) then the big guitar breakdown into the chugga chugga intro on geetar, followed by Sean Harris's flawless vocal delivery (how dare you diss him!)
and finally a superb, underrated guitar almost-outro by Tatler which just makes the song.
tl;dr: Metallica's version sucks, Diamond Head's rules!