I think I parked where Greywether suggested, then took one of the dogs and walked up hill up the footpath, it's not a footpath those are seemingly rarer than stone circles on this island, but just go up hill. I was actually willfully ignoring these chambered cairns intending to only visit the very nearby stone circle, but I apparently went too far up the path because before I knew it a large grassy mound stood before me, I couldn't ignore it any more.
But time is still just as against me as it was yesterday, there is another ferry with my name on it for this afternoon, so I was quick.
The higher (altitude wise) of the two cairns is a large grassy mound with some large blocks of stone on the top, next to it is a few stones set kind off circularly, could be a hut circle, or another cairn inserted into the side of the big cairn.
Down hill, slightly, is another cairn, presumably of the chambered variety, but on the ground it's another grassy mound with a heavier sprinkling of masonry on top than it's nearest neighbor.
There are other chambered cairns and more stuff besides over the hill but i'm looking in the opposite direction, for a stone circle, there are more than a few stone circles on North Uist but Burl in his bible only mentions two, and one of them is before me, I can see a white stone from on top of the lower (altitude wise)cairn I'll head for that.