Pretty much as described, the high summer weekend pattern for a number of operators was typically three round trips to the main Med points like Palma or Malaga, departing around 0800, 1500 and 2200. Getting back at 0500/0600 gave a few hours for quick maintenance and/or schedule recovery. The longer 3.5-4 hour flights to the Canaries or Greek islands were generally clear of weekends, you could get just two of these in a day. It was common for given destinations to be served on the same day of the week by all operators from all origins because this helped hotel arrangements and also shoulder season flight consolidation - Malaga on Friday night, Palma on Saturday, Fuerteventura in the Canaries on Wednesday etc.
Easily done from Gatwick, just about from Manchester as well, from Glasgow was a bit of a push. Reference above to getting four rotations in. This was done, maybe just for Saturday, from LGW/LUT only, out to the nearest points like Gerona/Barcelona. Court Line, until their 1974 bankruptcy, did this especially with their colourful One-Elevens, departures from Luton at 0800, 1400, 2000 and 0200.
A 737 or a new One-Eleven could manage this sort of high usage, Dan-Air with their secondhand fleet or British Airtours with their ex-BOAC 707s would generally need a bit more slack, although everyone tried for the maximum on Saturdays.
Actual overnight flights as described above do seem to have reduced, but nowadays you often find the first departures are much earlier, say at 0600, and aircraft are getting back to Gatwick still at 0100 or later, so things have just shifted a bit but utilisation is still high. In the 1970s-80s the equivalent German holiday flights were always like this, a whole platoon leaving right at 0600, someone once wrote "Germans refuse to fly at night". This impacted on UK operators as one of the major charter flight bases for them at the time was West Berlin, where Laker, Dan-Air and others had a number of aircraft based, often exchanging at the Mediterranean end if required. UK seconded pilots but German FAs.
In my experience Orion scheduled pretty much like the rest. But each operator had its own nuances it seemed; Laker got their One-Elevens to the Canaries, which seemed beyond the others. Britannia didn't seem to consolidate with the others as the season ended, unlike the rest. I'm sure each had just one or two wise sages in advance ops planning who had their own approach.
I used to accumulate my own summer season records of all this from various sources, oh for an Excel spreadsheet to keep it. In those older days my main recording medium was to write each rotation on the blank back of 80-column cards purloined from the computer department (you'll have to look these up if you don't know what one is). Made it easy to (hand) sort them by airport, destination or aircraft. Alas they have long gone the way of all flesh.