Can't honestly say that Feliway ever worked on severe anxiety (the Maxcat). I also tried rescue remedy in his water and am not sure that that did any good anyhow (the brandy lol?). I'm not sure that either is available in the UK but something that I found did help a bit with anxiety (short term) was homeopathic rescue remedy under-the-tongue human pills - used sparingly as they are sugar coated; and a herbal remedy given to me by a homeopathic vet, which if memory serves and it doesn't always/often, is called Biral. I don't think suitable for long term use either. I do wish there was a safe kitty calmer around. The french use a pill called Relaxine (sp?) but have not seen that here. They only use it for maximum 3 days anyway and only with certain cats.
It's very difficult because so few vets know how to cope with anxiety. Or say unhelpful things like it only happens cos they are a pedigree cat (sigh).
Lynn and Pinkbear you are so right though in that when they are ill or in pain, they can first-up show stress symptoms. When you take them to the vet, they are stressed from being there as well so it's a vicious circle.
Just remembered: catnip's a kitty calmer isn't it - once they've stopped vrooming? and vet claims valerian teabags in an old sock altho' not tried that one as can't find valerian teabags unmixed with anything else.