i got a '5 and 20 1' today. I took it to mean 1:25
Could there have been a "to" in there that you missed?
This construction doesn't seem to be used as widely now as in the past, but when I was a kid here it was quite normal to hear phrases such as "5 and 20 to 1" or "5 and 20 past 9" (which would be 12:35 and 9:25 respectively).
I would say that the majority of Brits faced with something like "A quarter of ten" will either not understand what is meant, will recognize it as an American usage, or quite possibly both! ("Er, that's American, right? What does it mean?")
You'll find too that using before or after might get you some strange looks, e.g. "A quarter after 3." British usage tends toward "to" and "past" exclusively.
Midday and "12 o'clock" are probably more commonly used in speech than noon, but I can't understand how anybody here could actually be confused by the use of noon. Again, I remember it being used widely in the past.
P.S. Oops! Forgot to respond to the original query. Whenever somebody here uses the simple expression "Half nine" or "Half two" it always means half
past the specified hour.