In reply to John Stainforth and John2:
While liners and proper gear can & will help.
There are other factors at play. What works on someone might not work with others. E.g. if you hav had frostbite before, you are much more likely to get frostbite again.
The casepoint that you could ski in -30 C simply means that for you it works. There are others, that it simply isn't the case.
To OP. Heated footbeds work, but there are differences. Also keep in mind that once you have them, they ain't that easy to move to another pair of boots/shoes. My friend got heated socks, which seem a much better idea. After all, those you can use with all boots (as long as the sock is high enough to get the battery compartment out of the boot).