I'm guessing that you have checked windows update manager?
Yeah, the best route would probably then be the manual installer. I installed it with the manual installer and it was a (slow) breeze once I had got the right file. Invade you are wondering which one it is from the MS website, unfortunately it's the large iso file. There are three installer inside the iso, so I would recommend you just open in it winrar and take the right one out rather than burning it to a DVD. Manual instals are generally better to do as windows update doesn't really give you much of a representation of progress.
Nb. The SP1 installer may seem that it's broken when staying on one point for ages, but it just takes a long time