The trouble with looking at Kings for this question is that they had political interests at odds with the Church. Henry II, for example, didn't care for the church ("would someone rid me of this troublesome priest") and may have been 'effectively' an atheist in that capacity -- probably one reason why his son, John Lackland, is noted as having similar views. But it is still quite a leap from "the King opposed Church power" to "the King was an atheist." From a philosophical viewpoint it is correct to generalize that Atheism did not exist in the middle ages.
It isn't that people just accepted what the Church told them. What did exist was heresy, and tons of it. You could throw a rock and find someone who technically did not subscribe to a number of proper doctrinal views and you don't have to go to the Renaissance or the Reformation to find it (just to find any movements that really stuck around -- thank you, printing press...)
The modern atheist, the late Christopher Hitchens, phrased this in a manner appropriate for the middle ages: it's not that there is atheism per se, but there is certainly anti-theism. People who wanted the church out of their lives or at least in a back seat. But a noble who came right out and said "there is nothing divine" or anything to that effect would probably be seized and set on fire, probably in that order.
Atheism as a coherent philosophical movement started with ancient Greeks but was dormant for a couple thousand years and didn't really emerge until the Enlightenment. The reformation and Henry VIII can't really be considered atheistic - just (again) anti-theistic in that they opposed the institution of the Catholic Church.
