I would place extremely large boulders to conceal the access to that crop, and stagger randomly placed smaller rocks to gradually lead back toward your paving. Keep the shape and flow natural looking with curves and backfill with river pebble a dug out trench that runs although it like a dried up river bed. This will be useful in wet weather, it will actually help direct the overflow of water that your property must suffer from. Possibly remove your storm water capping and repace with heavy duty steel mesh grate covered with river pebble. The sound of water rushing over the pebble and draining away will provide acoustics of a rainforest or running stream at the least. Use tall plantings to conceal this void space with tall palms or giant birds of paradise, strelitzias will have the look of banana leaves, and smaller strelizias will complement them. Plant densely so that it prevents access for little ones. Then use Clever lighting to focus a green oasis. Your limitation could possibly be an advantage in that the solution has to be unique. You may end up with a stunning water feature and private escape.

My other bush of Rhodys, taken today, I'm on top of the steps, it's about 6 ft. I've cut them back each year, they were huge when I moved in. Not good to have huge bushes near the house if there's a bushfire. The first bush has finished flowering. It's a hotter pink.

You refer to the Esther Dean method of layering various products and then using the no-dig method of gardening. I use the no dig method (without the layers that you refer to Trek) and keep adding waste material from my large native garden. Recycling as much as possible. But my method allows water penetration whereas often old carpet becomes water repallant and sheets of newspaper and cardboard can inhibit water penetration when they dry out. Eliminating pests often comes from stopping the use of insecticides and encouraging natural predators into the garden. Once you move towards sustainable gardening methods, the whole mindset falls into place. Hails I would suggest that you minimise manipulation of the site as much as possible. Also with sand, any plants growing from seed will become weedy. Plants germinate really, really well in sand.

@wuff Oh yes, the birds (and bees) are having a great time in the garden right now. I saw a group of five rather large and therefore quite heavy wattle birds trying to take nectar from the pink grevillea flowers on the end of the long spikes (2nd photo). The stems were twanging about like great springs and the birds were being flung all over the place, but holding on determined to stay put. Great antics to watch.