After lots of procrastinating I've started building. Working around other commitments, and the hot weather, progress is slow. I'm going with the name Swan River Railway because we're about 350m away from the Swan River. Seems as good a name as anything else I could come up with.
I've started cutting out the track base using 12mm marine ply. Below is a photo of the first few pieces laid out... doing that has definitely helped to visualise how big it's going to be, and this is only the first stage. The plan is to start with not much more than a loop around the tree, and then add more later. As you can see there are few plants to deal with. We had a truck load of free mulch delivered on Friday and I've started spreading it.