Yes, I understand "half ten" to mean 10:30. The confusing part is that in other languages a literal translation of "half ten" actually means 9:30! To be safe, stick with "half past ten" or "ten-thirty" when you say 10:30.

It's 10:30. It's ten-thirty. It's half past ten. It's half past (okay, if we both know the time is between 10 and 11). I've never heard anyone say, "It's half ten." If I did, I would think it was a clever way to say, "It's 5 o'clock."

If you're speaking with someone informally then 'half ten' is alright to say since it's casual speech or quite possibly slang. But I wouldn't use it in formal conversation. Also, somebody who's never encountered the term before might mistake it as meaning 9:30 or another time.

Yes, Half Ten means 'half passed ten.'

She's British. :) Now I got that it's British English. Thank you. :)