As the Heli is faster than the ship it needs to be used for the maximum possible portion of the route length - 300nm in your example. So yes the dispatch and pick up point are the same assuming no wind / current.
But ... what's the max [safe] range of the Lynx on its way back to Mother? Surely after launch the ship wants to be
there, to maximise the helo's speed advantage? If that's at the start point, then orbit port/starboard. If not, adjust for wind/tide .. which lies outwith the original question.