Opening few minutes were John Terrett from the second set - I assume it was during a lunchtime business roundup and the presenters had nipped out for some lunch. 'bout 1.55 it went back to news and it was John Nicolson with female accompaniment - can't remember who...
IIRC, when the news broke, it was John Nicolson and Valerie Sanderson on News 24, and Nisha Pillai on World (I know that one's right, as she missed the second plane hitting the tower). Gavin Esler was definitely called in, and I guess he was with Jane Hill on her usual shift. Similarly, for World, Nik Gowing was called in for about 6 hours until Phil Hayton came on (there's a few clips on http://televisionarchive.org/html/index.html from BBC World).
Thats a good site rob, even if a bit slow! Even better - it has the final World News bulletin before the Attacks - BSE top story!
Nisha even closes with "see you again in half an hour" at the end!
We saw her a little quicker than that though!
Yes, it's amazing to watch that last bulletin before the attacks happened - little did they know that the next half an hour would have implications that would dominate the news even to today.