[Bluecortina]

I seem to recall LNN TX was shadowing ITV for weeks before going on-air. The stability of the commercial LMS system was hugely important to Carlton/LWT and eventually was running at 99.9% performance.
LNN News did a far bit of shadowing but not everyday and often bulletins on some days and hour long shows another. The first few days of 1993 LNN actually transmitted LWT News branded bulletins. The launch of London Tonight brand was saved until Monday January 4th.
GMTV did a neat thing with distribution to the regions having "PresFax" type running orders showing timings to opt-out from NewsStar, but also Talkback in NICAM so the regions could all hear the St5 production talkback about late changes.

Just to add a little bit more. The original post 1993 tx suite was designed to be used by two companies and when a third was added out of necessity (GMTV) it became a bit of a headache. The 3 companies used different software packages to integrate their ad sales into some sort transmittable file solution into the LMS systems and their surrounding ingest machines. A third party software integrator company (Ken Louth) was taken on board to design and implement a solution. It wasn't easy at all and there were late/over night telephone conference calls between London (TLS/LNN) and the US (Louth) to iron out all the glitches. They got there in the end but I believe it was not easy. Just to add, GMTV's talkback was distributed in the teletext rather than Nicam and was affectionately known as Tit (Talkback in telextext). I can't remember which line it was added to. The regional opt out switching was added to another line.