This from Burl
"At the three henges at Thornborough in North Yorkshire, 'almost a straight line', the middle earthwork is 32m to the east of the line between the NNW and SSE enclosures. At priddy the centres of the thre henges form a 475m line from which the central henge deviates by 7.3m to the west. Even more exaggeratdely the unfinshed fourth henge is a full 67m off line."

They are substantially larger than Thornbro'
the smallest being 149-158m in diameter and the largest 170m compared to Thornbro's 92-97m.
Another difference is that the Priddy henges have no entrances and of course there are four of them, although the fourth is incomplete and is somewhat seperate from the group of three.