I know this is a slightly older thread, but for the sake of those searching this topic in the future....
When I was getting ready to come across with my cats 6 years ago (!), I also contacted the animal arrivals centre at my arrival airport (Manchester), and would recommend anyone do the same.
The woman I spoke with was very helpful and saved me a lot of time and worry - she was able to confirm that they had a reader for my kitties' specific microchips, and I sent her scanned copies of all their arrival paperwork, which she confirmed were all in order and would pose no problems for release on arrival.
It also meant they "knew" my cats before they arrived so it was particularly easy when I arrived at what's already a very stressful time.
Thanks Manchester!