Loosely based on Nottingham Victoria:
The Southern End:

The Northern End:

Baseboards not shown yet. The layout will have to squeeze into a space 16ftx4ft with hidden return loops at the back. As you can see, I have allowed a large build-out to the front of the layout for the southern turntable. This could be removed from the plan quite easily. The tracks in both tunnels would run on Peco Setrack 1st and 2nd radius for the sharpest curves possible to reduce space consumption, the tracks then running roughly under Mansfield Road/Milton Street.
I shall be using Peco Streamline and I'm hoping to achieve 7ft long platforms. (x4) I am dropping the bay platforms from my model to save on width and also to un-complicate the junctions at each end.
I shall update this thread with progress made. Next job is to physically set it all out using the Peco pointwork paper templates. Then I'll get more of a feel for how it will look!