Thanks for the reply tiompan.

I had a feeling I shouldn't of been too quick in linking the chambered cairns to hut circles. I'm not that great on timelines for old stuff.

Makes me wonder where the builders lived and in what type of structure. Close by the cairns or did they travel to the area just to build the cairns and live elsewhere, it's a puzzle like you say.

I remember passing a hut circle (Rhue) near Ullapoool a few years back they were digging at the time and got a few dates.
(http://www.wedigs.co.uk/c14results.htm)