With only half a day to explore and a bitter wind to contend with... and no map or guidebook, I hope I can be excused for not finding any ancient sites! However I did drive past the Culverwell site on the way out to Portland Bill. It sits right beside the road, which was how I spotted it, with a sign saying middle stoneage site (or something along those lines). All I could see as I drove past were two B&Q sheds and a larger wooden construction that was obviously covering something. The site was not open and you would have to walk to it from the car park at Portland Bill (pay and display) as parking on the road is not allowed.
For more information on site see links.