So, without further ado, the plan is as follows.
Its loosely based on New Plymouth, only mirror imaged and downsized. New Plymouth had an interesting set up, with the main station separated from the port with the loco depot 1/2 way between the 2. The layout fits the constraints of the available space.
(the following pictures are from the Turnball library (I think).
The main station sits on a curve next to the see. at the top left is the unloading yard, with a large good shed in front of that. the loading doors are covered to protect against the prevailing wind and sea spray.
The wharfs are also not particularly large. The one on the right is more interesting (and older) than the one in the center
So, using these photos as the BASIS for a layout I have come up with some modules that will fit into the room.
This has space for shunting and a short shunt to the port. The loco depot can be used to display locos not in use. The main station can also serve as a Junction and as wagon storage for an exhibition. I still have to do some thinking about how the station would fit into the car for transport.
There will still be some fiddling with the siding layout but by in large I think it satisfies most of my requirements.
Oh, and did I mention the beautiful troop station?