My best shots of Arbor Low were taken on cold, misty days. Being on top of the hill with the recumbent stones always left me with the wrong shadows on sunny days. Try to stay low rather than trying to get a shot from the top. Also, there are some interesting possbilities there for near-far composition if you're willing to lug a large format rig with you (something I wish I'd had when I was in the area).
I love the village of Castleton, especially early in the morning. Climb up to the castle for some interesting possibilities of both the castle and the surrounding countryside.