I can recall Major's resignation announcement also breaking into BBC1 at the same time - I think they took off Newsround, an episode of The Machine Gunners that Children's BBC were re-running at the time, and Neighbours.
That's right - I remember it was actually announced on Newsround as breaking news, then they went to another story, and thirty seconds later were faded out for a newsflash. That seemed quite surprising at the time because the convention those days was that you didn't do newsflashes during CBBC. As you say, a different era then in terms of news channels.
On ITV, they were showing England in the Rugby World Cup, so all they could do is put a banner on the screen, and eventually John Taylor the commentator read it out ("The players certainly not aware of that").
Blake Connolly and UKnews gave kudos