Hedge around old fort

I’m looking for advice in relation to planting a hedge around the circular rim of an old fort, it hasn’t any preservation orders on it of any kind. The previous bushes, whitethorn and blackthorn, were never trimmed and they grew to 20ft and more but fell over due to a combination of ivy, wind and livestock damage. The only problem is that the rim area is now very much in shade from mature Sycamore and Ash trees. Can you recommend a suitable hedge that will grow in partial and in some cases total shade until it gets established? I would prefer deciduous rather than evergreen with the exception of perhaps a few holly bushes and a few scots pine but if that is not practical I’m open to other ideas. The circumference of the rim is approximately 150 metres.