Below are links to rescue centres around the UK. Please note that although some places classify themselves as dog shelters or cat shelters they often get other little critters too. Give them a call and they will be sure to try and help you.
Dog Pages
Dog pages is a completely non profit site that has a very easy to use data base of rescue centres around the UK. Simply click on your area on the map and away you go.
http://www.dogpages.org.uk/index.htm
Cat Chat
for those of you more interested in the felines.
http://www.catchat.org/adoption/