I think its best if we just forget that bit about an earlier pair of boots. They are five years old, and I can't even confirm that I read the size right. Again, what I know for certain is that my foot with sock on is 27 cm long and 10 cm wide. I will use that chart to size myself. It sounds like I just misinterpreted the size of the boot I used to wear (it was too big for me anyway.)
Sorry for making this so difficult. I'm not trying to. Thanks for all the quick and helpful responses.