[Kojak]

I'd be interested if Philip did any network bulletins in the 1999-2003 era. I know he did sporadically between 2003-05.

Also, I've stumbled among a first clip I've found of Huw doing the Ten before 2003. I always guessed he must have covered at least once but this is the first I've seen:

www.youtube.com 

According to your Great Presenter Count of 2020, Huw presented a grand total of four (weekday) Ten O'Clocks before 2003 - two of which were in Washington for the 2000 presidential election. It seems George Alagiah was actually the most frequent relief presenter when both Michael and Peter were away (which itself was a rare occurence).

As for Philip Hayton, apparently not. According to Genome, the closest he got to a network bulletin between 99 and 03 was an edition of Breakfast on the day after the US election, which he co-hosted from Washington:

Breakfast
BBC One
Wed 8th Nov 2000, 06:00 on BBC One London

Presented by Sophie Raworth from London and Jeremy Bowen, Bill Tumbull and Philip Hayton from Washington DC.
Timetable on Monday (S) (W)