In conclusion, QI believes that this saying was introduced by
Richard Grenier who was attempting to provide a pithy representation
of an idea he ascribed to George Orwell. Later writers and speakers
turned his phrase into a quotation and directly attached it to Orwell.
Over time variants were constructed with modified phrasing.
Quote Investigator has a long article about this quote, cited in the Wikiquote page mentioned in a comment. They have many variations of the quote, from various different people including Kipling, Le Carré, Churchill, and Orwell.
Since you asked about those last two in particular:
In more recent years the saying has sometimes been connected to the
statesmen Winston Churchill. Here is an example from 2006:
While it may be apocryphal, Winston Churchill is often quoted as
having said (supposedly paraphrasing Orwell) “We sleep soundly in our
beds because rough men stand ready in the night to visit violence on
those who would do us harm.”
There are many quotes of Orwell's that are thematically similar, but don't quite match the words of your quote. For example:
In 1942 Orwell published an essay about Kipling in which he referred
to a phrase in the poem “Tommy”: 4
A humanitarian is always a hypocrite, and Kipling’s understanding of
this is perhaps the central secret of his power to create telling
phrases. It would be difficult to hit off the one-eyed pacifism of the
English in fewer words than in the phrase, ‘making mock of uniforms
that guard you while you sleep’.
In the same essay Orwell made a
statement about Kipling that thematically overlapped the later
misattributed phrase: 5 6
He sees clearly that men can only be highly civilized while other men,
inevitably less civilized, are there to guard and feed them.
Orwell referred to “less civilized” men above whereas Grenier later
referred to “rough men”.
See the article for more examples of this idea in Orwell's writing.