Are you looking for permenant evergreen shrubs such as fatsias and phormiums or seasonal plantings such as bulbs, pansies and summer bedding plants.
I have a mixture in exactly the same situation as yours (and in the SE)....some shrubs (fatsia, golden Catalpa, black bamboo, tree ferns.), a lot of bedding and a few exotics such as gingers and japanese bananas (musa basjoo).
I find that planting the bedding ones up with dark blue petunias which give a lovely sweet scent and orange marigolds is a lovely display. Add a few small pots of night scented stock for those warm summers evenings and you can't loose.