Making plans for my current layout

I got the basic idea for the demonstration line for the Cardiff Road area *first part of the "mainline" if you will*. The other stations of the mainline route will be Cardiff Bridge Street & Cardiff Junction, Cardiff Junction connects with the branch line and that area will go up a somewhat steep gradient and make a gentle downward slope so engines can ascend & descend with ease and then will end at Cardiff Halt, which has a demo shunting area. The main yard will be at the Cardiff Road end and will house quite a good few engines *for my layout I mean*.