Visit your vet and have the dog vaccinated for rabies. A fortnight later (or a month for some vaccines) return to have a blood sample taken. There are four vaccines on the market and not all generate the required immune response at the same rate. The ideal time to take the blood test varies. Something to discuss with your vet. This blood sample is sent to have the level of antibodies measured. Some vets advise a second vaccination after a fortnight - to be 100% sure of a positive blood test. You will need to discuss with your vet his preferred regime. If the blood test proves positive your dog can return to England six months from the date of the blood sample being taken, not the date of the test. If the test proves negative a further vaccination injection is needed and the blood test repeated. 90% of the time a single vaccination is all that is required. It is a bit of a gamble - but the odds are stacked in your favour if you go down the single vaccination route.
Once the blood test as proved positive revisit your vet who will be able to issue a pet passport - having first checked the microchip.
You can now go abroad with your dog, but it will not be able to return to England before the six month period is up.
Add your foreign address / contact details to your dog's tag
Before your dog can return to England you must take it to a vet, between 24 and 48 hours before you embark on the ferry or board the tunnel train. The dog must be treated for tick and worm and the passport signed, dated and marked with a time by the vet.
If you are traveling to an area affected by sandfly - the Mediterranean for instance make your dog wear a Scalibor collar for a fortnight before you go. Sandfly is the vector for Leishmaniasis a disease that cannot be cured properly and for which there is no vaccine, prevention is the only option. This is not an insect restricted to sandy beaches but found in parks and gardens in town.
That is it; save having to pay a surcharge for 'administration' to the carrier. Easy money for them as the dog stays in the car during the crossing and no apparent 'administration' is undertaken.