Despite the fact that "Liam" is a derivative of "William", it's also popular in Ireland and I don't believe that many Irish names ever make it to the Sloan lists in England. Last time I was over in England, there did seem to be an inordinate number of "Zoe" Sloans -- and Zoe is of Greek origin.
I wouldn't be at all surprised if "Nephele" someday becomes a Sloan name over there. It's got a certain ring to it that hoi (British) polloi don't have generally have. What do you think, Priapos? :)