It's only "old-fashioned" because we aren't properly taught how to speak in primary school. I myself rarely use it, cos none of my childhood peers did, but my mum taught me it.
Interestingly, it's fairly widespread in the countryside and West of the UK! The n functions as a mouth shape to allow the sound to flow more easily.
I think this rule also applies to the word "the", pronounced as "th" before a consonant, and "thē" before h or a vowel.
Yes, you bring up very valid points. My mom was a stickler for correct English but outside the house it's so easy to follow the crowd.
We naturally just change our pronunciation for the the before consonants to "thē" before h or a vowel. Non-native speakers have to be instructed. But at least in the printed form, there's no problem as with a/an.
Thanks for your contribution.
As I have already explained. Both "a" and "an" are correct. But if this was a 'choose the right word' we can only give one word. That would be "a''
If it is an exercise where you type in the words then you can use either "a" or "an" since we always allow British alternatives.