Hi OpenIntro,
I am in the process of going through the PET scheme to get two dogs over. I found the articles in this forum very helpful "Pet Scheme for Dummies" part 1 and part 2. The website you should go to in order to find an accredited vet is on the Dummies Part 1 thread. I bumped it up for you. The link to the website is in the very first post of that thread.
When you locate the USDA VS for your state, give them a call. Ask for the "Export" office. Give them the name of your vet (not the office name, but the actual name of your vetinarian). They can tell you whether or not he or she is accredited. You can also just ask your vet. But if you want to make 100% sure, call the USDA VS for your state.