It's alright about posting in this one, this is meant to stay prominent. I'm glad you've discovered the theme tune, Chris, it is, as you put so well, in a world of its own. There is an interesting story behind the creation of the original tune back in 1963. A woman named Delia Derbyshire slaved for hours and days to construct the theme painstakingly using equipment that was being used for a function whose time had not yet come. You can read the story
here. My favorite version of the theme is of course Delia Derbyshire's 1963 original... nothing could ever compare to that, and I'm glad Murray Gold built on top of that to make the theme for the new series. If you listen, every element from the original is there -- but new elements, like the drums and the strings, have been added over top. Magnificently done. The one problem with the new theme is that it lacks the bridge section of the theme. This can be clearly heard in all the versions above, but we have yet to hear it in Gold's new series theme.