Here's how my Carmina sizing breaks down:
Alcudia (shoe) - 9.5 UK (Best fit, snug but not tight)
Rain (shoe and boot)- 9.5UK. (Comfortable fit). Heel is wider than I'd like but no pinching anywhere. Overall, a very comfortable shoe, not tight anywhere.
Robert (boot) - 9.5UK. (Comfortable fit). I wear with thick socks in the winter and fall. I think with a thin sock I might be able to wear a 9UK but I haven't been able to try one on. 9.5UK would still be comfortable...