What traditional hedgerow plants are OK in full shade below trees in UK ?
The soil location is roadside and poor, and we want to infill between established trees which will shade the location. A traditional country mixed hedge with colour and berries would be good if shade is acceptable.
"Traditional" hedgerow plants are sun loving. Under the shade of trees and with competition from tree root systems is not the best growing conditions for most plants. You may encounter problems in the long term for both the shrubs and the trees. Imposing competition for water and nutrients is usually not a good idea. With shade, competition, and combine that with alkaline soil from the chalk, the list will be greatly narrowed.
But if you are determined, and you know how to practice good soil and water management and to neutralize the alkalinity, you might find some possibilities for shade plants to suit the purpose in this listing from the Royal Horticultural Society.
You may want to take the list to a local garden center and see what is available and maybe get some tips from a local nurseryman, gardener or landscape designer.