Serious thoughts on what to do?

I am having very serious thoughts on what to do in my garden. I love the lush tropical look but I am very conscious on just how much watering is needed to keep it looking so good. I don't have a problem watering, in fact I quite enjoy it, but water is going to become a precious commodity so we are being told and I would much rather drink it than pour it on the garden.

A view down by the pond.

I have 5 very substantial water butts, not you ordinary 210 litre ones  mine are all 500 litres plus. They are also very nearly empty!

In hindsight, (a wonderful thing, but very annoying) when we had the bio mass boiler installed and had the new patio laid, we should have had a huge tank sunk under the patio as there are 3 roofs that fill just one large water butt, I believe the would have easily filled a sunked tank!

So what to do??
The arid bed just loves the baking sun, I do nothing to it, as you know, occasionally if I am walking past with the hose it gets a bit of water but to be honest not much at all. So do I make the rest of the garden like this? I would have to devise a way to protect it over winter though and that is fairly hard work to set up.

Even the palms, this is my Butia, above,is suffering.

The Ensete Hiniba should be way bigger than this.

Persicara is wilting.

The Maureli, is still a bit stumpy!

I have a decision to make. I don't have and probably won't have grand children, but the rest of my family do, I could easily say 'its not my problem' or 'it doesn't affect me'! But I have to live with myself. I think it is ludicrous that we flush 'drinking water' down a toilet to empty it when we are surrounded by sea. This has been a bug bear of mine for years.

Back to the garden, even though the girls dug in a load of manure the soil is dust dry, I am seriously considering changing the left hand side as you look up the garden to a gravel bed, a bit like at Beth Chatto's gravel garden. The link will take you to the gravel garden gallery, beautiful, but? I am not sure its me. Ideal for my garden and situation, but do I like it? Mmmm??? The jury is still out!!! More thought needed.