Trev,
It's good to see that you are thinking about your layout again. A man needs his hobbies
The layout I am building at the moment has a "fiddle yard" at a lower level to the main scenic part. Most of the sidings are hidden but the entrance/exit points are all easily accessible from the front so that I can operate them manually.
My previous layout also had a lower level "fiddle yard" so as you can see I am quite a fan of the idea.
Although part of the "fiddle yard" is visible I find that the eye tends to be drawn towards the more scenic parts of the layout.
There are some photos/plans of my old layout (
called Sustenbahn) and progress reports on my new layout at
www.swisstrains.net Just click on the "N-scale model railways" links. I know that it is probably not exactly what you had in mind but it might give you some ideas.
John