In terms of Thornborough, the cursus came first, possibly three of them. Then a neolithin "mortuary" enclosure perhaps 100 years later. after about 400 years they built the henges, a further three to five hundred years saw the burials come along, closely followed by the post alignments. in all the complex took 1500 years to build.
All I'm getting at is that for all we know they started out as for one use and ended up for another.