There is indeed a kink in the Stonehenge Cursus at the western end, which bulges its overall width to 150m ish at the widest point. The southern bank then heads almost perfectly due west to the far terminus of the cursus at Fargo. Julian Thomas believes that this was the 'original' cursus orientation, and pointed towards Beacon Hill. I don't agree personally, because it's only a very small section of the ditch facing that way, while the rest of it (and the entire northern bank) point a little further north.

I don't think its been decided yet whether Amesbury 42 long barrow at the eastern end came before or after the Cursus, but one is certainly aligned on the other. The Cursus is also aligned on the Cuckoo Stone, which was probably a natural deposit about 1km further east. Its roughly aligned on the equinox sunrise as well. Woodhenge almost certainly came later, but has been aligned on the Cursus/cuckoo stone alignment whether by chance or design.

As for the A303, well not quite; the A303 points a little further south as its magnificent beauty rolls west across the landscape!