News 24 play this countdown every hour. Sometimes the countdown is longer, sometimes shorter depending on the timing of the preceding trails. The longest I've ever seen is 42 seconds (but I don't watch News 24 at 59 minutes past the hour all the time, honest).
The countdown is accompanied by a lovely tune, really funky for the news. It cleverly builds in the classic 'pips' into the percussion. Such news music hasn't been heard since the days of News Review on BBC2 and ITN's news music 'Non-Stop'.
There's a bit of a countdown in MPEG format to your right.
The full version is 90 seconds long, and the stereo MP3 of ths can be downloaded from here, or a smaller-filesized mono version can be downloaded here. (Thanks to Mark McMillan)