Posted: 10/08/2016 at 07:37
I don't think there is much available outside of professional packages, there was one available on the GW site some years ago but it was quite limited and clunky to use. There is a program called sketch-up that you could download for free, you can use that to do plans in 2 and 3D, Maybe you could google and see if it's still available, it's not something that you could 'run with' straight away so you would need a guide/manual as well.
Simplest way is to draw a scale plan of your plot on paper but then use tracing paper over the top to draw out any ideas. That way you can make lots of changes or play with ideas without having to re-draw your scaled plan each time, saves time and as you can use more than one layer of tracing paper at a time you can mix and match bits of your ideas until you settle on a design. Also if you print your photos A4 size on ordinary paper you can draw some of your ideas onto them to help visualise how any changes might look.