Looking at those two clips, I've noticed something a bit odd.
In the music clip, it clearly shows the News at Ten set in the same studio they used for the national news (i.e. next to the atrium) which was later used for the ITN News Channel and now London Tonight etc.
When Trevor did his side shots, the newsroom would be clearly be seen behind him.
However, in the rehearsal tape, his side shots show a blue screen - suggesting that the set had been moved to another studio and that they keyed the newsroom on.
Would I be right in saying that the set was moved? Possibly when they got a new set for the main ITN programmes (ie. the blue minimalist set with a yellow stripe on the desk (red for the evening news)?
Yes, I think you're right, Earlie37, though trying to figure out old ITN studio usage is a bit of a nightmare! News at Ten did leave the atrium in the mid-1990s for (I presume) one of the basement studios. At the same time, the voiceovers were re-recorded. They used to be "From the headquarters of ITN, News at Ten with..." but once the programme left the office surroundings, they were changed to "From ITN, News at Ten with...". However, between 1992 and 1995, both News at Ten and the Early Evening News used atrium-side sets. Quite how they managed this is a mystery. I'm assuming that at one point they had another studio next to the atrium, as it would have been impractical to constantly swap sets twice per day. Similarly, I've never been able to figure out where Channel 4 News or the News at 5:40 came from once ITN moved to Grays Inn Road. I know Channel 4's current studio alongside the atrium was only constructed in 1999, so they must have been elsewhere before then. At the moment, there's no Studio 3, so I'm guessing if that existed at one point, it's been removed somewhere along the line. Although ITN only occupies a few floors of the building now, I believe they initially owned the whole thing, so presumably there were other studios on other floors, especially when ITN produced so many different programmes; many more than they do now.
That video of the NAT music is interesting, as the bong is wrong. That's not the one that was used on air. ITN must have supplied that themselves. I always thought the pre-1992 NAT theme was the best of the lot. Hewson's two versions (1992 and 2008) don't sound as powerful as the original did.