While I still haven't settled on a layout to build I thought I'd show you the original layout my Dad built. Amazingly, given the number of hours I spent playing with this layout and the number of photos my Dad took while I was growing up we can't seem to find any photos of the layout in use so you'll have to settle for just the track plan.
The plan came from the 5th edition of Hornby's track plan book, which was originally published in 1979, and is described as being a Triple Track Layout with Sidings. Three trains can run continuously or each can run into the siding area for shunting. The train on the black circuit, running clockwise, must stop at the signal A to allow either of the others to reach the sidings. The R.047 switch and isolating rail in the engine shed allow an engine to be isolated so that the remainder of that siding may be used by another engine.
We didn't use the isolating rail, but three sidings were plenty for supplying trains to and from the three separate loops. We also didn't have the same buildings and signals as in the diagram but at the time (and now) I didn't care about that as running the trains was the best bit! Also the more buildings there were the longer it took to set everything up as the layout was stored behind the wardrobe in my bedroom so everything taller than the track had to be removed before it was put away.
It was an excellent layout that gave me hours of pleasure, thanks Dad!