Hi Roger, With the pleached trees, I think your underplanting amps up the tropical look especially if you go with a magnolia that have the dark green upper leave and the bronze underside. You could just go for banana or palms - personally I think you might be right about the clumping bamboo becoming a bit dense. Regarding your 400mm retaining wall - citrus are shallow rooted and tend to have a root system that goes out to their drip line. Maybe if you put it in a corner you can use the corner to espalier it in conjunction with staking it to get upper stablility but I'm not sure how it'd go with the roots - but give it a go at $30-50 depending upon size it's not an huge amount if it doesn't do well - just dig it up (just watch the thorns) and give it to a friend - check out Daileys for varieties and maybe get in touch and see what they think, they might do them on a dwarf root stock - I've found them to be helpful in the past. i'd be reluctant to underplant any kind of citrus though - as they are shallow feeders.

We built a pool exactly the same, however we didnt use laminated glass but a monolithic piece of 80mm thick Plexiglass 3mx2m from Germany. This reduced the overall cost of the pool considerably. Pool was fantastic and doubled as a water feature when not in use. Incorporating LED lighting allowed the pool to take on the mood of the night. The only downside we found with the pool was that after heaving swimming and sunscreen the waterline of the Plexiglass would need a clean. Other than that it gained lots of comments and was even used for photo shoots and promo work.

I would hire a local landscape designer who will work with you to come up with a plan including pool location. They are quite cheap really and great value. You don't need a $15,000 set of landscape plans just some basic plans with plants, pool and cabana locations noted. Then have a local draftsman prepare the lot for council. The rectangular pools always look a bit bland on paper but once installed and landscaped they are still the preferred choice for me. I would look at other options away from glass, way too much cleaning! A standard pool handrail will work equally as well or perhaps use individual recycled hardwood timber posts in ground spaced apart to comply local regulations. I would say that would suit your already great garden and tie in with the Lomandra's. On a side note, find where the services run.... sewer lines, easements, etc.

my suggestion would be to add a big deck (with pergola outdoor kitchen etc) at the top of the stairs and cover the steps with timber decking to match with the deck to one side or the other depending on direction of the sun into the house...it's not the height of the retaining wall that's the challenge it's the mountain of earth behind it that's the problem....is the retaining wall in good condition, does it flood during wet weather..you shouldn't attempt to change retaining wall with without consulting an engineer and moving that amount of earth would take for ever by hand and you risk an avalanche while it's being dug out...consider the deck (and decking over the concrete path as a much more usable space better connected to the backyard)