Possibly Primula x polyanthus hybrids, maybe Iceland poppies--in a sheltered, relatively sunny spot--or maybe some kinds of English daisies (Bellis perennis). Those are the ones that bloomed best over the big winter of January 2011, here in Arizona.

Lots of choice.

Dwarf conifer for the middle, a few ivy round the sides for trailing, some silver dust for the top if you can get it, a few polyanthus, pansies and violas for underneath, don't forget bulbs too...maybe some dwarf tulips of daffs and crocus and snowdrops. There's also lots of small foliage shrubs around too such as dwarf Euonymous.

It's not clear whether you normally just use pansies on their own, or whether you are mixing those with other planting, as Andy has suggested above. The fact is, even 'winter' pansies don't flower in the proper winter - when the days are dark, long and cold, they'll just sit there, waiting for better conditions, which is why they often look at their best in March and April, at the end of winter.
If you're not using foliage plants, Andy's suggestions are spot on - you really need to rely on foliage for a continuously attractive display throughout winter - flowers, if they arrive, are just a bonus.

I find my winter flowering Pansies/ Violas, stop flowering in December and have at least a 6 week rest before they flower again.
But I do find baskets/tubs can still look good all winter if using a mixture of plants and bulbs, So I put Primulas, Ivy, a slow growing pale conifer with Spring bulbs such as Lilies, Narcissus, Chionodoxa, Tulips, Crocus - all came in miniature forms and flower consecutive months starting with Snowdrops. Use new compost but there is no need to feed till the spring and water sparingly in winter if at all!

in addition to the above there are also trailing heuchera/heucherella/tiarella. cant remember which it is. I know 'plantagogo; sell them. Vicky is also a member on here. google them and see what they have.

Also= Skimmia and cyclamen alongside all the above.

Thanks everyone very helpfull indeed