Just thought I should share my experience now that it's done. I took everyone's advice and took 400mg of ibuprofen about an hour before my appointment. Instead of the 5 minutes that I was meant to be in there, it was more like 45. The first time she tried, the dye all came back out on the table. Second try, same thing. Apparently I have a roomy lower 2/3rds of my cervix. Anyway, a balloon catheter and $100 later, the dye went where it was meant to. The worst part of it was that every time, just before she was going to inject the dye, she would take out the speculum, which meant that to try again, she had to start again. But although the speculum bit was uncomfortable, just the same as it is for a smear test, the rest of it - I didn't feel a thing, not when she grabbed my cervix, not when she dilated my cervix to get the catheter where it had to go, nothing. I didn't have blocked tubes though, and from what I can gather, that seems to be the main source of pain for people.
Anyway, all is A ok for going ahead with IVF... which I'm starting my meds for tomorrow!