Cate,
I second Kathy's recommendation for Nupercainal. It's an ointment that has excellent numbing qualities, and you should be able to find it in your local pharmacy. The generic name of the active ingredient is dibucaine.
I also use Calmoseptine, but I find it Calmoseptine works better for me when I use it to prevent butt burn rather than treat it. In other words, if I know I've eaten something which will cause me trouble later on, I'll apply some Calmoseptine, as it helps to "seal off" the area. But as you've read, there are people for whom Calmoseptine is useful in the midst of butt burn. When I have butt burn, I usually stick to Nupercainal to blunt the irritation.