This is my favorite, from Prince Caspian:

"Where's that _______ balley Rush got to?"

hail aslan we have com aslan
once an king ore qween alwayes aking ore qween

Great thread. I love all the sayings in the Narnia books. Here are some more:
"By gum" (I'm pretty sure that is in there somewhere)
"Great Scott"
"Nothing for it" (That one is interesting because it sounds like it would mean for them not to do something but actually it means for them to do it). I think it is in the books. It is in the BBC version of LWW but when I look at that spot in the books it wasn’t there.
"Look sharp"
"I'm jiggered."
The use of "jolly" (often used for emphasis)
“Bother”
“Time out of mind”
“Soup and celery”
“Beards and bedsteads”
“Horns and halibuts”
“Bulbs and bolsters”
“Whistles and whirligigs
“Logic! Why don’t they teach logic in these schools” (Anything could be substituted for logic)
“I wonder what they do teach them in these schools”
“Sharp’s the word” (sharp can be replaced by other words)
“I shouldn’t wonder” (especially helpful for dire predictions)
*tears herself away from the books; otherwise will spend the whole day finding sayings*
I'll probably post more another time.

"Oh bother! I've left my ________ in ______________!"
"Smell of hot _____, smell of hot self..."
"And what a filthy smell of _______!"

EDIT: I have more!

"It's worse than what ______ says about living at the mercy of the _______!"
"This one is in need of a little hot chocolate."
"I do believe that's a/an ________!"
"Don't ask him what that _______ thingummy is."
"Some kids who play games about _______,
got gradually _______ and ________!"

9/10ths of these are common British sayings

Some from me:

Beards and bedsteads
Cobbles and kettledrums
and what ever else the "dlf" says

9/10ths of these are common British sayings

That makes sense since Lewis was British. I figured a lot of them had gone out of date though.

and what ever else the "dlf" says

Here are some more D.L.F.isms:
"Tubs and Tortoiseshells!"
"Giants and junipers!"

"Beards and Beadsteads."

"By Jove"

"Great Scott"

Very interesting language, can you imagine talking like this in these days...that would be really something!

But you can imagine in a 100 years, they'll be looking back on texting and IM and be saying, "LOL"? How weird is that???

"I could order you to have it destroyed!!!"
Sorry, guys, I don't remember if that was original to the FotF Radio Drama or if it was actually in the book.

9/10ths of these are common British sayings

That makes sense since Lewis was British. I figured a lot of them had gone out of date though.

Some of the sayings Lewis tried to use, had gone out of date even when he wrote them. He had read them in Edith Nesbit's children's books from the beginning of the century. Friends who knew children better than he did, could tell him that children don't talk like that any more.

And when he found better contemporary sayings, they would be sixty years old now, and some of those would have gone out of date, too ...

Wow. Y'all already got quite a list there. The only other one I can think of is 'Blighter'.
This one isn't from the books, but ever since Mr. Beaver used it in LWW movie, I've wanted to.

I like this saying by C.S. Lewis "If I discover within myself a desire which no experience in this world can satisfy, the most probable explanation is that I was made for another world"

I know the classics “He’s not a tame lion.” and “By the lion’s mane.”
There is also the Calormen saying, “The sun appeared dark in my eyes.”

And whenever I get annoyed/sarcastic I start spouting out (in my head) "O my father and O the delight of my eyes, may you live forever, but you have Utterly ruined me!". That's two sayings, I guess.

I wrote a letter to a friend and called my sister's dog a "Record Stinker". Practical usage of the saying.