dogwoods - nothing easier. Dig a trench in autumn and line out hard wood cuttings. They will relish the clay and look fantastic too, especially the variagated C.sibirica 'elegantissima'. Pyracantha can be espaliered and pleached on wires - a great evergreen 'fedge'. Also, blackthorn, prunus cerasifera, hawthorn, haze - all easy to prpagate, great for wildlife and good to look at. Finally, try some roses, especially some of the rose species (burnet, nutkana, primula, cantabridgiensis, rugosa.