Unpaving

[Jacob]

Basically if you lift a few slabs whatever is underneath can be turned into soil.
Even solid concrete slowly develops soil cover starting with algae and mosses and slowly building up with wind blown debris, worm and woodlice action etc.
Natural processes can be speeded up! Chances are you will able to dig out some or all of it of it and all you have to do is bung in some compost.
Our last very nice garden was on an abandoned back yard (chapel school playground) of compacted chippings on top of a deep layer of rubble. No soil at all but by the time we got there some 50 years of natural processes had added a thin layer of soil and a dense cover of grass and weeds. You speed the process up by adding organic material. Cardboard is good for starters!
We found that even substantial fruit trees can grow in thin soil - the roots spread wide but shallow, never much more than 6" down.

 

[Spectric]

Another option is walling without the mortar, just stack .

https://www.tobermore.co.uk/homeowner/applications/walling/

 

[DrPhill]

Going back to your initial post and the suggested option of the more formal, raised brick beds. Don't rule out this option and consider dry walling as a diy solution. These are specifically designed for retaining. This would avoid a massive amount of heavy work excavating hardcore, clay etc.
https://www.wickes.co.uk/Products/G.../Paving+Walling/Walling+Wall-Bricks/c/1000716

By dry-walling you mean they can be assembled without mortar? That sounds very interesting, though there are plenty of ugly bricks to contrast with. I will look at their catalogue and see if there is anything suitable. It means more organic shapes are possible, and I only need to lift one block at a time. So tedious, but easy.

Great idea. Thanks