Further to my last: I would strongly suggest that you contact the Liverpool Dock Port Authority as soon as possible. They will need to arrange a clear space for you to land. Working docks are complex areas, with potentially all sorts of vehicles moving around in all directions, and obstacles in places convenient for the loading of a ship, but likely very inconvenient for landing a helicopter. This event is not the norm, and the sudden unexpected arrival of a helicopter overhead would be alarming to say the least.