Considering that Christian commonly refers to someone who accepts that God sent his only begotten son, Jesus Christ, into the world to save us from our sins, and that an atheist is one who does not believe that God exists, Christian atheist appears to be an oxymoron. Perhaps you could elaborate on their beliefs.
As for George Orwell in the example you gave, the fact he attended an Anglican church would not make him a Christian.
I would consider myself a christian Atheist.
I do not believe in God/heaven/hell.
I believe all religions have value to Human kind.
I believe in the values Christ has taught.
I put my Kids into CCD class so they can learn about religion(specifically my families)
I go to church with my family.
I help out the church as time allows me.
I am a lector (I like reading the Old and New testaments).
I do not hide my beliefs if asked.
I would be interested in your thoughts on this.