In Shakespeare's play Henry V, there is a Welsh character named "Fluellen." This is an anglicization of this name, the "fl" being an attempt to reproduce the voiceless "ll" sound of Welsh.
I agree. I love this name and I'd still spell it with the double L, but I'd just pronounce the double L like a single L. I don't like double Ls in Welsh. :)
In D.C. Simpson's comic "Ozy and Millie", Ozymandias Llewellyn and his father (just known as Llewellyn) are sovereign rulers of Llewellynland (ie: their house and yard). Llewellyn is a dragon and therefore responsible for many of the world's conspiracies. http://www.ozyandmillie.org.