Is this the correct thing to do in
No, it's entirely wrong.
With that timer instead of a thermostat, there will be no control of the room temperature.
What will happen is the boiler will switch on at maximum and stay that way until the time runs out.
Result = overheated rooms and vast quantities of gas wasted, and then the rooms cool until someone bothers to stab at the timer buttons once again. Probably the most inconvenient and inefficient use of a heating system ever known.
Realistic options:
1 - use the thermostat that's there properly. This means setting it to the room temperature required and leaving it there. Constant adjustment is not required, it will turn the boiler on and off as the room temperature varies.
It's also set to 30C in the picture, which is ridiculously hot. Try 20.
2 - If it's necessary to have different termperatures at different times, such as cooler at night, then replace it with a programmable thermostat. That can be set to have different temperatures for different times of the day.
As with the existing thermostat, it's set it once and leave it that way.
3 - If you want the same temperature when the heating is used and also times where no heating is used at all, it can be done with the existing thermostat and a separate timer. However the programmable thermostat can also do that, so buying a separate timer doesn't make much sense.
4 - For people who go out of the house leaving it unoccupied and are incapable of setting a timer, devices such as the Nest / Hive / Tado will control the heating for you by detecting when your smartphone is not in the building.
Only of use where everyone has a smartphone and also has the app installed. Otherwise it's just a very expensive programmable thermostat.
im assuming the temperature of the heaters is from the boiler settings?
The boiler settings are for the maximum temperature of the water circulated through the radiators. That is unrelated to the temperature of the rooms.
It's also another thing that should be set once to something like 55C when the boiler is installed and never changed.