Just from the pictures and plan it looks like the stones are from a very solid hut circle, the size would suggest that as well, if it's not the size and stones make it more likely to be the kerb of a robbed barrow, it's the old map thing where any circle of stones found is at first called a stone circle [in a way they are] but not a stone circle in our sense of the word, I'll be interested to know what you think when you get there though as i respect your knowledgable opinion Mr Watson:-), it's something for sure so anything old they've found is great.