It's getting a bit late, but try Godetia, Candytuft, Virginian Stock and Nigella, which are all fast growing. If you get early frosts, that's it, as they're annuals. They should give you some late autumn colour, all being well, but not winter - for that you'll need to visit your Garden Centre and choose winter bedding plants. There will be plenty quite soon.

If you buy young plants rather than just seeds many people like pansies and violas, which you can plant in autumn and will bloom in milder weather well into the spring.Its too late to grow them from seed this year. Or you could go for winter flowering heathers which have quite a long flowering season in early spring.

If you want reliable colour in the coldest weather variegated evergreens are your best bet as nothing much flowers then - have a look at the varieties of Euonymus Fortunii. These will grow happily in tubs for some years and are bright in the dullest weather.

Also for colour don't forget bulbs - there are different daffodil varieties that bloom from December in mild areas right through to April, so read the flowering time on the bulb packaging. The little species crocus flower early in a sunny spot, followed by the bigger ones. Follow these with early and then late tulips and this will see you through until its time to put in next year's bedding plants.
Happy gardening!

Many thanks for taking the trouble to answer. I think I need to plan in future but some great ideas to think about.

There are winter flowering shrubs which are a joy to see, and many are scented too. I have a Viburnum x bodnantense ‘Dawn’ which lifts my spirit in mid-winter and I also hanker after a Hamamelis x intermedia near my back door. For more ideas take a look at http://www.rhs.org.uk/Plants/Plant-trials-and-awards/Plant-awards/10-AGM-plants/10-AGM-winter-flowering-shrubs .