Personally I say as you can't be told off for being non-canonical here you should go with whatever you need. I wanted Xander to be cut, but Spike not cut for the latest part of Catamite - they did a bit of docking - so voila, they were what I said.

The popularity of circumcision in America has dropped in later years, but it is most likely that Xander is cut and that William was uncut (yes, I've actually researched it - and it's not that I just like reading about cocks).
:)