Very true about buddleia. I like the idea of species roses, too. To go smaller, I was also wondering about lavender though, if this is really a cliff, then presumably it has to cope with cold, salt winds. The RHS recomend the following for these conditions.
Euonymus japonicus (Japanese spindle) – dense bushy evergreen, good for hedging H 4m (12ft), S 2m (6ft)
Olearia macrodonta AGM – vigorous, evergreen, daisy-like fragrant flowers in summer, H 6m (20ft), S 5m (15ft)
Rosa rugosa – vigorous, deciduous, fragrant carmine-red flowers followers, orange-red hips, good for hedges H & S 1-2.5m (3-8ft)
Tamarix tetrandra – arching branches, scale like leaves, pink flowers in late spring, good for poor soils, H & S 3m (10ft)
Hippophae rhamnoides AGM (sea buckthorn) – bushy deciduous shrub/small tree with spiny shoots and silvery to bronze leaves, female plants produce orange fruit, H & S (6m (20ft)
Elaeagnus x ebbingei – dense evergreen shrub with dark or metallic sea-green leaves, H & S 4m (12ft)
http://apps.rhs.org.uk/advicesearch/profile.aspx?pid=472
