In reply to DavidR:
It's a bit hard to be emphatic about what boot might be best since there isn't (as far as I know) any sort of objective test, but I'd reckon you'd likely find the Sportiva Batura/Scarpa Phantom Guide all-in-one type boot a bit warmer, without getting quite as bulky or expensive as the Spantiks.
I had a similar problem and got some Raichle boots of this type a few years ago, and haven't had nearly such cold toes since. Not sure whether it's just due to more insulation, or a better fit, or what, but they are definitely an improvement over my old boots.
It might be worth having a look here for lots more detail about some likely candidates:
http://coldthistle.blogspot.com/
(you'll need to look back to the 2010 posts)
It might also be worth mentioning other factors - having no belay jacket, having cold hands, getting sweaty and body-belying sitting in the snow have, I suspect, all contributed to my cold feet in the past.