Probably the toughest one that will tolerate the conditions you mention is Prunus laurocerasus, commonly known as cherry laurel. There are a few varieties of this plant now,some with narrower, neater leaves. It does get quite large though at up to 25 feet with a spread of up to 10/12 feet over time. Cotoneaster cornubia is semi evergreen, has red berries in winter, but tends to become tree like over time. Berberis varieties (make sure you choose an evergreen one - the purple/red and yellow leaved varieties drop their leaves in winter) will also tolerate those conditions,but they do not get quite so tall and are thorny - Berberis darwinii gets to about 8 feet tall.
As the soil is clay and probably turns to concrete in summer when it dries out,unless you can keep them very well watered right up to end of October, all of these are best planted in autumn.