Alchemilla mollis (Lady's mantle):
Bright green soft leaves and a froth of acid yellow/green flowers in summer. Very easy for ground cover. Height to 30cm.
Briza media (Lesser quaking grass):
Semi-evergreen grass with beautiful delicate dangling flower heads. Short lived perennial but it will self-seed around. Up to 70cm.
Persicaria runcinata 'Purple Fantasy':
Attractive foliage perennial with triangular leaves with V shaped dark purple marks. Loose spikes of pink/white flowers in summer. Hardy. Up to 60cm.