The actual transport bit can be tricky. Flying means that special arrangements would have to be made for your dog to travel in a cage, in a heated hold, as freight. That can be very expensive (and potentially very stressful for the dog).
Cross-channel ferries are simpler but your dog has to remain in the car throughout the journey. You're not allowed access to the car decks during the crossing but, if you gave him an extra long walk first, he'd probably sleep all the way.
Assuming that you're going on holiday, rather than emigrating, one of the trickier parts of the procedures is that you must take your dog to a vet in France (or wherever you're travelling from) between 24 and 48 hours before your return journey, in order that he can be treated against ticks and tapeworm. That means that you've got to find a vet to do the job. The DEFRA website helps by providing a link to the French Yellow Pages (together with instructions on how to search for vets) but it obviously helps if you speak fluent French (otherwise misunderstandings might occur and your dog could be barred from return travel).
Full information can be found here:
http://www.defra.gov.uk/animalh/quarantine/pet s/index.htm
Chris