Could be Barrow Docks, but what is going on and when?
There are two doors in the bow – you can see one is open. The ship is in a dock where the water is at a fixed height. It is not in a tidal dock or harbour as would be the case for Heysham or Stranraer where ferries use a linkspan which can adjust to tide height.
Looks like a road shipping container is being loaded - straight in off the quayside. Looks like a few are already on the deck of the ship.
The ship is identified as ex US built, Royal Navy tank landing ship HM LST-365, acquired by British Rail for the ferry service between Stranraer and Larne in the 1950s who named it Mowbray Road. Source: Tank Landing Ship LST (navsource.org)