Lots of evergreens grow well in pots, but look for ones that have that little something extra to give during the darker months. Sarcococcas for example are sure winners, as their flowers will fill the air with with their sweet perfume throughout winter, while winter flowering heathers will add a blaze of colour.
Skimmia japonica ‘Rubella’ is another all-time favourite. Its a male skimmia, so doesn’t produce the glossy red berries of the females, but instead you get conical clusters of red flower buds that appear in autumn and persist all the way through to mid-spring, when they finally burst open.
For added height, top a large pot with an obelisk and let Clematis cirrhosa var. balearica scramble all over it. The lightly freckled flowers look pretty against the fresh green foliage, and will also keep bees and other pollinating insects coming back for a nectar fix in winter.