You can (or you could in April 2011) get to the location that the photo was taken from by going down the steps and into the tunnel at the back of the cleft where the steps terminate.
To get the the putative slate quay you would have to swim or, if the tide is out, climb down to the beach from the bottom of the steps (hand line useful) and then climb up onto the 'quay' from the beach. There is a shaft (blocked by a wagon stuck in it) from the open quarry down to the quay.
Dave