I'm always shocked that so many wear a 10 in running shoes, but are several sizes smaller than me in cycling shoes. I may wear my street shoes too tight compared to other people, but it doesn't seem like it to me! Size 11 street shoes are too long. Could't possibly do that, but hearing Catrin, who is quite petit, wearing size 10 makes me wonder what the heck I'm doing.
I tried on a pair of men's Sidi's in a 43.5, and they fit. The 43 were too small. There didn't appear to be an issue with the heels in Sidi's. Just the price tag!