The rule about "an" before "h"+vowel used to be: always; you'll find it in the Bible, e.g. when Moses tells Sarah to take "an handful of meal".

More recently it was: use "a" if the first syllable is stressed, e.g. "a handful"; use "an" if the first sylable is unstressed, e.g. "an historical novel". This applies (if you apply it at all!) even when the "h" is voiced, as well as when it's unvoiced, as in "honour". The French make the distinction, even though they never voice their aitches: "l'hiver", but "le hibou".

"Hotel" is problematic because both syllables have equal stress, so it's not incorrect to say " a hotel", but it's not pedantic (if your'e a bit old-fashioned!) to say "an hotel".

The modern trend, of course, is to use "a" in front of all cases where the "h" is voiced. I'm fifty-two; I'm English; and I went to a Grammar School that was founded in 1554: I reckon that entitles me to be a bit snooty about the way I write, if I want to be. (But not the way I speak!) I don't have a problem about any of you not wanting to be pedantic if you choose not to be. (And one of Cleary's characters says "could have" later on, so I know he knows better!)

That's enough: it's nearly ten o'clock here time to put the kettle on. (And woe betide the first one to ask "put the kettle on what?"!

Steve