any of the medium sized architectural ferns would look stunning. Begonia sutherlandii is a gorgeous orange flower, fully hardy and would 'flop over the edges'. It is also a shady lady and flowers late summer.

I find Tiarella less susceptible to Vine weevil and there are some leaf forms.

small leaved lamiums with white or pale pink flowers would 'glow in the light shade.
Vinca minor white flowers/variegated leaves would also soften the hard edges and trail.

Thanks you Seaburngirl, will have a look through your suggestions.

Although I’m not a begonia fan I really like the look of begonia sutherlandii and will be trying to source it online as it’s not readily available. Ne er thought I’d ever grow begonia’s but never say never……

it is the only begonia I grow :)