I was wearing a pair of Endura MT500 overshoes at the time which got soaked through. It could be that it was a very wet day and puddles above your ankles mean water will find a way in.
Andrew I have found the Northwaves to be a very lovely boot, however I was unable to get my extremely wide feet in. I have in the past tried the MW80 and bought a pair of diadora chili boots again could not get my feet in either of these (even tried 2 sizes up on the MW80's as I was desperate to have a pair). It is unlikely that the RW80's will fit therefore.
This is why I usually stick with Specialized and have a pair of Specialized defrosters which are anything but warm, so would probably stay away from the road version if one exists.
Besides the overshoes recommended (are they now Pro Endura H20, if not where can I get the ones recommended) are there any other winter boots I can consider??