There's a Wessex giant called Bevis, who legend has it used to walk on the sea bed an was able to walk to the Isle of Wight from Hampshire across the Solent. There's a couple of long barrow attributed to Bevis (Bevis's Grave; Bevis's Thumb etc) that I'm aware of.

Not sure of any alignment/correlation with Orion though other than the the easterly orientation.