Autumn: asters, japanese anemones, heleniums, grasses, eupatropium, sanguisorba, nerines, cylamen, autumn flowering crocuses, camellia sasanqua, hydrangeas. Trees: cherry trees, fruit trees for fruit, figs, autumn fruiting raspberries. Acers for autumn colour and a Japanese feel but they dont do much the rest of the year.If you have trees with edible fruit you get spring blossom and Autumn fruit and often Autumn colour as well. I would only get an edible cherry tree for instance.
Winter: cornus, garrya elliptica, mahonia, chrysanthia edgeworthia, winter flowering honeysuckle, clematis jingle bells, clematis wisley cream, snowdrops, hellebores (lenten rose), grasses.
Evergreens are useful eg ferns, yew, box etc
Topiary is nice.
Espaliered fruit trees look good in winter