If you have a modern boiler, there should be a thermostat on your hot water cylinder as well as a room thermostat which will mean that although you may have the hot water switched on, the boiler won't actually kick in unless the tank needs heating and will stop heating the cylinder once it's hot through so I do think you are at risk of overcomplicating the settings slightly with all these on and offs.
There may be a case for having the cylinder heated just before you actually need the hot water, and with an insulated cylinder it may well be enough to just have it set to come on for an hour before the first shower and set to go off an hour after the second shower which will hopefully leave enough for your shower and washing up during the day. The only way you'll meaningfully reduce gas usage by reducing the time hot water is on is if you can avoid getting the cylinder red hot and then not using that heat so that the cylinder slowly goes cold (for example overnight) without the water even being used, though bear in mind that heat is probably being lost into your house and so is not a complete waste.
My feeling is that your boiler is unlikely to be a particularly complicated model and may run more efficiently if you try to get it to heat both hot water and radiators at the same time rather than first one and then the other, but there really is not a lot in it, and it sounds like you are already doing this anyway.
As for the heating, it's probably worth reading the meter (all the digits, even the red ones after the decimal point) and seeing whether you can use less gas to get the same amount of comfort having the heating on from morning till night. This actually depends on the property, and some houses seem to be better with the heating on permanently rather than try to keep warming up them from cold and for other houses the reverse is the case. The only way to find out is to run the experiment and there may be as much as 10% at stake. You can also play with having the room thermostat on at a lower setting rather than switching off completely (at night, say) and this may mean that when your thermostat is set back to the higher temperture you'll find you're comfortable at a lower air temperature than you would be if you were sitting in a hot room with your back to a stone-cold wall. If this works, you might consider changing to a programmable thermostat so you you can set different temperatures to apply at different times.
That said, I get the impression your one hour heating period is so you can snuggle up to the radiator in the morning and then once you're up and about you may not even be at home, or you don't feel cold if you are. If so, although the heating may be less efficient used in this way in terms of gas use per unit of useful heat, your overall gas consumption may still be lower. Sometimes fancy technology is never quite as effective as manual control used intelligently, and you can of course do the meter reading test.
What if you have a gas cooker?, you may be wondering. To be fair, any heat from the cooker is likely to come into the house anyway, but unless you're baking cakes all day one day and eating sandwiches the next, I don't think the normal variance in gas used from day to day in the kitchen is likely to be significant enough to throw your experiment in a meaningful way, particularly if you run the experiements over a few days.
As far as carbon emissions are concerned, the important thing is that we don't get caught in what has been referred to as Micro-Changes Bull----. So do bear in mind that while home heating is an important consideration, don't get so worked up about it to the point that you forget an annual flight you might be able to avoid entirely has a similar impact. There's a really interesting free book you can read online or download at this website: David MacKay FRS: : Contents - https://www.withouthotair.com/
Some of the data is not as up-to-date as could be hoped for, due to the untimely death of David MacKay, but it is still a valuable read and much easier to read than than you'd imagine given the complexity of the matter.