Best Solution to warm up that cold floor:
My mother is old and was having a hard time walking on them cold tiles, so a buddy of mine, fixed us up with about the best way you guys can imagine, and we did not have to pay through the roof to get radiant heat, nor did we have to go through some kind of a program to qualify, our total cost is negligible both for up front cost on equipments and almost nothing extra on our electric bill:
He happened to find one of those pads used to heat a water bed, it's flat, thin, you can throw it under a rug, and best of all it's under 300 watts, oops, no I mean the really best of all, he got it from the Salvation Army for under 5 dollars, and told us "Merry Christmas " when we asked him how much we owe him for such a solution, I have never encountered such a comfort stepping out of the shower and onto a warm rug, he had the thermostat bulb right on top of it, and we had it plugged in , hidden from view, we even had couple of guest asking us how can we afford radiant heat "based on my disability check " we really had them going.
try it , you'll love it, from what I understand you can get these things on eBay.
Good luck !