Guerilla gardening advice

[Kmetsch3]

Hello
The area I’m trying to beautify is a north facing slope, mostly covered in ivy (and take away packaging), full of bricks and building site spoil (from the 1930s) and has a few sycamore trees

I’ve had some success with bulbs, clematis (there is old metal fencing for it to climb) and forsythia.

I’m wondering whether plastic tubs could be the way forward.

Does anyone have any suggestions to add colour and interest?

Wargrave Cranesbill geranium is a good plant for spreading and self seeding. There are some other varieties of this type of geranium that are invasive and would spread around.
Achillea Mollis might survive, although it prefers sun.

Might periwinkle work? Apparently it's good on hopeless slopes

Hellebores for the winter and forget me knots or lily of the valley?

Watching for suggestions...