Its been suggested LWT news was moved to 5.15 in September 1992 to give more prep for the new programme starting in Jan 93 or to allow a On buses repeat at 6.30pm to bring in more viewers.
What I actually think is, everything was moved around to allow the switchover to come back into being for the last couple of months.
I don't see how moving the news to 5:15 gave more prep for London Tonight. Nor do I see why they'd rearrange their schedules just to bring back an in vision handover for a few months. Especially as it meant having to fudge the end of Children's ITV every Friday to fill the extra 5 mins.
The main change then was that LWTs hour long regional programme at 6pm didn't return that autumn, in anticipation of the start of London Tonight at 6 in January. So presumably they took that opportunity to make Home and Away the same time 5 days a week.
Doesn't explain why they chose the news to be on at 5:15 rather than 6:30 like Thames though. Maybe they wanted a last chance to start the evening with a non-news programme? They were probably restricted as to what could go over the changeover, I can't see either wanting their others regional programme on their airtime