Hi Gordon,
Just to add to the already excellent advice, if it's a nice day then it's worth walking around the edge of the port from the beach/prom area, plenty of cafe's to provide you with a good start to the day and I find it easier on foot just to stop and pop a camera in the many and various places you can get a view from. It is a bit of a walk, will take you about an hour or so but can be worth it. I usually did it on a Sunday morning and provide you use common sense you will find a few open gates where you can stand and get good views, obviously PLEASE DON'T be tempted to wander onto the dock estate!! There is also an open area near the fish market area. And if you looking for a different shot, try from the multi storey car park near the Maritime museum where you can get a photo of anything moored right up in the city centre berths.
The other bit of advice is that there are NO facilities up at Tory, so make sure you have supplies.
Hope you enjoy your visit, it's a busy port and there are usually plenty of movements, some of them just internal port shifts, but you won't get bored.
Andrew