I used to absolutely love this as a kid. My high school music teacher introduced it to me when I was about 13 and I was blown away. I've been listening to it a lot recently, it's really inspired a new song I've written- especially the intro and theme most well known for The Exorcist.
Anyhow, here's a really cool live performance of it from 1981. It's in 3 parts, links to the other vids on are on the page for those who dig it. It's really beautiful in parts. This could be quite easily covered and made really cool, especially the "heavier" sections if you monkey around with them a bit.
YouTube - Mike Oldfield - Montreux 1981 - Tubular Bells part 1a