Just a word of caution - at least on the E46 cars if I remember correctly, the 3 nuts that hold the front spring hat onto the tower brace need to be replaced every time (and they are expensive). The reason given was that BMW uses a special stretchable nut (the torque being very low).
I'm not sure if this is fact of myth, but I think if I went to the trouble of replacing the springs, I'd spring for new nuts (pun intended).
