Gary Terrza has been an announcer for Channel 4 since 1991 (having previously been an announcer for Central and CITV presenter in the 80's). Peter Offer has been on BBC TV since I think 1990, although he left a full time role at the start (literally) of 2011.
I think, in fact, Pamela Ballantine has been at UTV (albeit only as freelance these days) for longer than Julian. She started in 1983. I suppose she had a fair amount of time away from continuity though.
For a shortlived period they occasionally showed shots of the announcers in vision during the announcements, just for the hell of it. As parodied on Paramount with Phill Jupitus announcing while naked.
I joined STV as a Continuity Announcer in March 1976 (after a spell of voicing trails) and am still announcing at BBC Scotland - that's thirty-seven-and-a-half years.
The only announcer who can lay claim to an TV announcing career in the UK as long as Tony is Redvers Kyle - from September 1955 to January 1993 - firstly at Rediffusion (until 1968), and then at Yorkshire afterwards.