Many thanks to all the help so far, it's got me well into this now.
Thanks to the chap that sent me the 6x4 two tier layout. I set up a mock layout using that design (or as near to as I could get). However, I just couldn't get enough traction on the 0-4-0 to pull more than two (small) carriages up the incline - even after a small redesign to lengthen the incline. It's this loco that was intended to make this run too, as a small hillside route.
I have now abandoned the 6x4 layout, and have rebuilt it as a 6x6 with a central access panel. I decided to invest in track layout software for my Mac (RailModeller), and using that I have now managed to design a rather busy plan, but one that I'm happy with. It gives me two main lines, a passing loop, and a branch line on the outer part of the circuit, and I have an inner circuit with a compact loop with sidings off it. My plan is to make the outer lines as passenger routes with two or three stations, and the inner circuit as either a rural line, or perhaps a goods yard.
I'm currently making a switch panel, using two rows of switches - upper for points, lower for track objects (such as lights). I have some LEDs and I bought a set of two way momentary toggle switched from CPC.
Picture of it here (if anybody is interested):I've yet to decide on the final details of where to put things like the control panel, and the controllers. I intend to make this a fairly open plan layout, with only a small amount of relief detail, but mainly an open countryside kind of look. I also haven't worked out where to put things like track breaks.
Anyway, it's been fun so far.
All the best.