Isn't it where it is because of the lattitude?
The sighting along the pairs of station stones at the soltices(?) form a pair of parallel lines. Something like one sights W to E the other E to W.
If all four stones are joined up they make a lovely rectangle, something impossible from lattitudes further to the north and south. (which would give you a wonky rectangle instead).
They knew back then that it was hip to be square.