At the rear Buddleia globosa and the normal one and the black elder with a small tree either a rowan or a hawthorn, in front cotoneasters,cotinus(grace)
berberis and pyracantha grown up an obelisk to give you something to control it with
Viburnum tinus, a variegated phormium, agree on the variegated dogwood, and at the front if it is a brightish corner lavender or senecio greyyii and sarcoccus confusa, if you still have room squeeze in a hammamelis mollis and a lonicera fragrantissima for more midwinter fragrance and flowers.. that collection will give you loads of insect and bird activity