Garden planting notes for rear garden side border

To help you design the planting or additional planting for your garden or flower borders, your GardenAdvice MyGardenTeam gardener has created these notes for you. Next with your input we will create a planting plan
The brief for the rear side border
To create a classical English or Scottish summer flowering herbaceous border with a modern twist of lots of drifts of different colours, mainly using plants such as agapanthus and salvia, possibly some drifts of Echinacea and later in the year Aster’s.
Normally with herbaceous perennial border, we would add some feature shrubs for structure, but I was thinking this time we would mainly stick to herbaceous perennials or perennial plants and just have a few feature shrubs such as some red and yellow cornus stem plants at the rear to add some interest in the winter plus a few helleborus at the front to provide some later winter flowering.
Style and example pictures
The style is very much a modern English or Scottish herbaceous border with some roses and clematis obelisk


Proposed plants.
Agapanthus africanus Albus
Agapanthus africanus Big Blue
Agapanthus Dr Brouwer
Campanula lactiflora alba
Campanula lact. Prichard’s Var
Echinops ritro Veitchs Blue
Epimedium versicolour sulphureum
Euphorbia wulfenii
Helleborus niger red
Hosta Canadian Blue
Hosta siebolidana Elegans
Iris pumila Lily White
Iris pumila Pogo 2 Litre
Nepeta Dawn to Dusk 2 Litre 3
Penstemon Hewell’s Pink
Penstemon White Bedder
Perovskia atriplicifolia Blue Spire
Persicaria microcephala Red Dragon
Phlox carolina Bill Baker
Phlox paniculata Blue Paradise
Phlox paniculata Flame Coral
Polystichum Plumosomultilobum Densu
Rheum palmatum tanguticum 5 Litre 1 5
Thalictrum delavayii Splendide 3 Litre 2
Verbena rigida 2 Litre 3
salvia caradonna
rudbeckia goldsturm
Roses clematis
Clematis on frames
Other notes
Leak pipe
Mulching
Spring staking