Foxy had a fear almost that bad at our previous vet. she would have to be carried in and out because she couldn't/wouldn't walk on the floor there. When we switched vets, I couldn't believe how much happier she was to go. Funny thing is the last vet never did more than the basics with her. Miki has done invasive tests, surgerys etc and it was still Foxy's favourite place to visit. It came down to the floor.
Another big part of what changed is that I was allowed to be with her for most things except the surgery. The techs were very matter of fact, patient and never made her do anything that scared her.