I am in the middle of preparing my three dogs and one cat for transportation to the UK. I'll post my experiences here to help others going through the process.
Well, the first step is microchipping your pet (cat, dog, ferret) at least seven months prior to travel. The first problem you'll encounter is trying to establish which kind of chip should be implanted.
I called the DEFRA helpline (+44 870 241 1710 (Monday to Friday - 8.30am to 5pm UK time)) and they were extremely helpful. They said that customs at both Heathrow and Gatwick have universal chip readers that can read 99.9% of all ISO chips meeting specifications 11784 or Annex A of ISO standard 11785.
My vet was very helpful and pointed out that there are two main chips here: AVID and TROVAN. The latter is not ISO standard. The former has two forms - ISO standard and non-ISO standard. Unfortunately, the kind used in Taiwan is non-ISO standard. But there is a third kind which did not have a name but was ISO standard. Basically, an ISO-standard chip will bear a 16-digit number. Non-ISO-standard chips bear a 10-digit number.
So, you have two options to consider: (a) get the non-ISO-standard chip and buy a reader to take with you on the plane to assist customs, or (b) insist your vet gives you the ISO-standard chip. Personally, I think (b) is the best option, because if your pet was ever to get lost in the UK, you'd want the chip to be readable by people other than yourself.
My pets already have TROVAN chips, but for the NT$200 - NT$300 per chip, I'll get the ISO-standard ones put in as well.
Get the vet to check the chip is readable before and after insertion. All vets must read the chip and verify the number at each of the next steps (which I will update you on as I go).
The next step is vaccination against rabies. (Remember, the microchipping must be done before getting the rabies vaccination.) The post about vaccination will follow, but if you have any questions about the process, you can call a very helpful Dr. Fooks at +44 (0)193 235 7840 or the DEFRA helpline number listed above.