There are a number of websites that have a lot of information and images of our many breeds of British sheep.
The British Coloured Sheep Breeders Association has a very good introduction to our coloured sheep, including some that may surprise you. Their list of the different breeds has information, images and links to the individual breed societies.
The National Sheep Association has a full list of 86 different breeds found in the UK, with a description and photograph of each breed and link to the breed society.
The Natural Fibre Company 'Meet the Animals' page has more detailed information about the wool from each breed, although the list of breeds is shorter.
The Rare Breed Survival Trust website has information on rare sheep breeds