There are also some words derived from French but pronounced in a very non-French manner. The t in valet should be fully pronounced. Making the word sound French is a non-U hypercorrection.
> Making the word sound French is a non-U hypercorrection.
I disagree that pronouncing it "VALLay" is hypercorrection. Proper French pronunciation would be "vallAY" (with the emphasis on the second syllable).
At any rate, my language background is upper-middle-class English English, and nobody pronounced the word "valitt". That's an americanism, as far as I'm concerned. As a consequence, I've always struggled with the word when used to mean cleaning e.g. a car interior.
FWIW, I understand that the "U and non-U" thing was meant as a joke, was horribly snobbish, and was anchored in a particular stratum of early 20th-C English society.