The Pet Travel Scheme 

The Pet Travel Scheme allows dogs and cats to travel abroad, and return to the UK without quarantine.......subject to very stringent criteria. The official DEFRA site gives up to date information on the following link:

http://www.defra.gov.uk/animalh/quarantine/index.htm

Also you can find some very helpful tips on the use of the scheme at:

http://www.ledogstop.com/ledogstop/pets.html

The above site gives some useful contacts on the other side of the Channel.