How does one correctly pronounce the letter 'H': "Aych" or "haych"?

What is the correct sound of the letter H when reading the alphabet - is it 'aych' or 'Haych' ?

The Cambridge Online Survey of World Englishes has the question, "How do you pronounce the letter 'H'?"

Their current results:

aitch (85%)
haitch (12%)
I use something else (2%)

You can see a clearer (and navigable) image of this response map at the link above by registering and taking the survey:

According to the OALD, the standard way to pronounce the H is this one, which is without the "H" sound in its pronunciation.

Although on Wikipedia, it says there is also the other pronunciation (with the "H" sound at the beginning) which, anyway, is considered to be nonstandard.

How can we say one is more correct than another with evolving pronunciations? At which point does haitch become improper and aych is "correct", or vice versa? An article the BBC ran in October 2010 mentions some interesting class separation issues as well.