Mini-diggers are fun for sure! Specially if you're used to shifting tons with a spade. Weeks worth of spading done in a day or too, whilst having the opportunity to toot the horn and do doughnuts. Controls are a bit tricky to get used to and they are prone to toppling over if messing around too much or not thinking.
Our garden: -
The house was built in the 1920's, the hardcore they used was clinker from the local iron foundry - which is caustic pebble like grit. They also seemed to have dumped some of it on the garden. The soil was also full of broken bricks, concrete and, weirdly, large animal bone chunks.
Someone had then crazy paved over that, planting gigantic 20kg+ lumps of sandstone around the edges.
!Someone else! had tarmacked over that!
And the icing on the disgusting cake, concrete on that! A gigantic amount of not soil.
When I was about 16 I started picking at a crack in the concrete. Not long after, I had an electric road pick chiselling away at it. Then a hydraulic pick.
My brother and I worked so unbelievably hard to shift the stuff with a sledge hammer, pick axe and wheel barrow. We ended up filling three or so ?10? ?12? ton skips over the holidays.
A minidigger was the final thing used when I'd given up on the spade for grading through the clay and digging up old foundations.
Once back to the soil / clinker, I then had to rotovate it all, mix sand and nutrient into the clay to break it up. It was so compacted a builder through it was concrete.
Large amounts of time were spent picking bricks and rubble out of the soil by hand. The rotovator helps and doesn't at the same time.
It will catch on rubble and broken brick, and pull them to the surface. I'd then either grab them by hand and chuck them into a bucket or wait for the sun to dry the surface out and rake the surface.
With that bank in the photo, maybe the brick doesn't go all the way down? Maybe someone has dumped crappy soil on there to save disposing of it? Especially if it's not the same lower down, near the grass.
Provided the soil isn't just rubble, quite a lot of plants will grow on it. I've seen 3ft high buddleia growing out of brickwork!
Either way, I would probably shave some of that bank down to make it look less like it's scooping up the wall so high. You could either take it right down or go down less and have someone lay some extra brick to raise the wall a bit.
For weeds, you want to cover all of the exposed soil except where the plants you want are growing through. That can be done with pebbles, bark or landscaping fabric. The first two are out if you don't use a surface somewhere near level.
They can also be a bit expensive. But you have to factor in for how much weed killer costs, applying it and making sure it doesn't also kill or harm the plants you want to keep. Whereas the coverings will last for a long, long time and are virtually a one shot thing. Golden or yellow pebbles tend to look really nice against flowers and grass and work better than bark for weeds.
The fabric, you'll probably want to cover that with bark or something if you don't get the entire bank covered in flowers, because it looks pretty nasty on it's own.
The same is true of indoor plants. Quite a lot of them, particularly herbs, will grow mould and become infected with fruit flies if the soil is left exposed in the warm house. Basil from the supermarket is mouldy almost as soon as you get it home. You can prevent it by covering the surface with sand or tiny pebbles so none of the soil is left showing. Although it's not really worth it with basil since the plant is destroyed the first time you use it to cook anything - despite what those lying TV programs try to suggest about 'growing your own' (which only works if 'your own' if a big greenhouse or verge of it).
Shifting the soil is going to be hard work. But at least it's simple work. It's not like wiring a house up or doing the gas yourself.
If you have any sons over the age of about 14, buy them a RoughNeck spade and a wheelbarrow.
If they complain, remind them that's it's like going to the gym, but free!
RoughNecks are the ones with bright yellow shafts, and about 15 - 20 quid. They're extremely hard to snap. I went through loads of 5 pound ones. They all bent or just snapped in half. So it's worth getting the more expensive one that'll last.
No sons to hand? Ask the neighbours for a loan of their kids maybe? My neighbour did the same thing with us when he was laying a new drive. We were about 10, 12 and 17 at the time and it was good fun to do some grown up work.
There aren't THAT many weeds there and there's not that much soil. I can't see that much rubble in it either. A few guys should be able to clear that quickly enough. Push the wheelbarrow right up to the wall and drop the soil straight it.
If you stick some cheap trelis up along the back, you can plant some fast growing climbers like Clematis along there to cover the wall in flowers and colour.