What if we treated the sloping site like a gravel garden, and planted with spaces between the plants?
Miscanthus ‘Malepartus’, 1.8-2m; purple flowers; average growth speed; cut down in the spring
Jarava Ichu, 60-90cms; white flowers July onwards; semi-evergreen, fast growing; comb in spring (alternatively one of the Pennisetums)
Libertia Grandiflora,evergreen, 70-90cms, white flowers in May
Carex Testacea, 40-60cms; evergreen; comb in spring
And on the building side – Cornus Alba Elegantissima which has red stems in the winter.
We need to include large daisies – Rudbeckia Deamii?
And then we could add pops of colour along the borders with alchemilla and nepeta to pick up the blues across the path.
And we still have sedums and bergenias in hand!