The reason for showing the same episode twice in a day was started by the BBC with Neighbours. School kids were apparently bunking off school to watch it, so the BBC decided to repeat it at 5.35pm and the rest is history. When ITV acquired Home and Away they did the same. Home and Away's second episode of the day was mainly shown at 5.10pm in some regions or 6.00pm in others.
In fact when Home and Away started it was only on at teatimes, it was about a year in before they started screening it at lunchtimes as well. The first lunchtime slot, I remember, was 12.25 because kids in my class used to be able to go home and watch it in their lunchbreaks and leg it back to school for one o'clock. They moved it to 1.20 during the Gulf War when the News at One was extended and became the News at 12.30 again.
Since this thread seems to be turning into some sort of record of Home and Away scheduling, Granada started it at 5.10 but moved it to six in January 1990 when Granada Reports became Granada Tonight and moved from six to 6.30 (which was possible as Emmerdale's network slot moved from 6.30 to seven at the same time). Then in 1992 they moved it back to 5.10 and Granada put regional shows at six, including Blockbusters, Families* and an hour-long Granada Tonight on Fridays. But that flopped as in January 1993 they moved the regional shows back to 5.10 and Home and Away back to six. Then in January 1997 they moved H&A back to 5.10, Granada Tonight to six and regional shows at 6.30, until they got fed up of the effort a year later and just did an hour-long Granada Tonight.
That * in full, then. Families was an odd one as it was mostly networked at 3.25, and Granada, as they made it, did an omnibus on Thursdays at 10.40. However for some reason Granada decided not to show the network screenings after a while and only showed the omnibus. During 1992 they screened it at six o'clock for a bit but when that slot ended they didn't go abck to 3.25, but went back to showing the omnibus alone. I remember the last ever episode was an extended 45 minute show, which neccessitated moving the 3.20 news bulletin, so Granada had to put a cartoon on to fill time. So the only region not showing Families in its intended slot was the region that made it.
Granada also persisted with the Corrie omnibus after the regions dropped it in the early nineties, and when they launched daytime repeats of Corrie in 1993, Granada didn't take them and stuck with the omnibus on Sunday teatimes. They used to reschedule the ITV shows like Dr Quinn Medicine Woman and The Cosby Mysteries for mid-afternoon and put the omnibus on at 6.30. They never showed the Monday episode in this omnibus, by the way, just Wednesday and Friday, so if you missed Monday's, tough. They had to eventually stop when the Sunday episode started in 1996.
Of course, a few series were only shown in a few regions, Granada and Carlton alone showed Granada's stupid CofE soap Revelations, and in return, Granada showed Carlton's awful London Bridge for a bit.
In the nineties, Granada also did what no other region seemed to do and take Granada Tonight off for two or three weeks in August, and instead do a five minute bulletin and fill the rest of the time with Laugh With The Carry Ons. Surely the North West generated enough news in August for a proper show. It's quite a big region!