The Chelsea boots have always been a difficult step in my imagination, however since i met these Chelsea's i had to revise my opinion. Wearing it day after day it get's better and better. It feels soft and gives a good support. The weight is also very good, light, but still it feels good almost strong. The soles are very comfortable and the wrist has a good volume, so with a medium high wrist you can enter it.
Compared to Classic Achilles it happens sometimes people size one size up if they are using already the maximum volume of the Achilles.
If you are not sure, just ask.
EU size 43 = US 10 / 10.