After the gyno said I had to go to psychosexual counselling, I returned to my GP. She didn't feel that full-scale counselling was necessary in my case, but she did decide to send me for cognitive behavioural therapy. I had my first session in early January and am expecting to have my last session next month.
It has been very helpful. I am feeling better in myself and more relaxed. After a couple of sessions I no longer felt so ashamed or upset about the vaginismus, and I didn't feel like I was defective. For this alone, I think it was worth going to CBT -- I still had the problem, but I didn't feel so bad about it. But the aim of the therapy was to actually cure the condition, and I'm pleased to report that this week my partner and I successfully had sex for the first time in over a year. There was some pain at first, but we took it very slowly, with him backing out every time it was uncomfortable, and finally it didn't hurt at all, and... it was a lot of fun :)
I know that the problem might not be completely gone yet, and I know that this approach won't work for everyone. And I certainly don't want to criticise dilators or physical therapy or any of the other treatments people use; I didn't try them, and they might well have worked too. But I think it's important to know that CBT does work for some people, and can be an option worth considering.