You do not say what boiler, so to improve the existing system it depends on what your willing to pay, and what boiler is fitted.
Hive works well with boilers with no option for ebus control, but you have two options if using Hive.
1) Fit two Hive single channel units.
2) Fit one Hive single channel unit and Hive TRV heads.
A electronic TRV head does the same job as a motorised valve, but instead of hard wired switches, uses a wireless link. You could leave the motorised valves in place, and just link them both together, easier than removing them, but you need a method to control which rooms are heated when, and the big problem is Hive TRV head costs around £54, so with 8 radiators in a house, that gets rather expensive.
There were 6 months ago cheap eQ-3 and Terrier i30 TRV heads which could be used in some of the rooms, to reduce the total cost, but with Brexit they seem to have dried up. They were some adds at under £10 each, but no more it seems.
If the boiler is OpenTherm enabled then EPH do thermostats that work as master/slave with your existing system.
There are two ways to control a modern boiler, one with ebus, the other with return water, with the latter there is a problem that a standard TRV can't turn boiler off/on it can only adjust output, Hive is designed to bridge that problem, so the TRV head sends a "demand for heat" to the wall thermostat, which then allows Hive to turn the boiler off when not required, but more to point on when it is required, and although the Hive wall thermostat does measure room temperature, it is really a hub which connects all rooms to one control using the signals from the TRV heads.
In real terms there are always rooms colder than others, so in some cases just 2 Hive TRV heads are enough, the rest can be stand alone, in my house I have 9 stand alone programmable TRV heads, and no linked head, and my problem is hall cooling time, it is too slow, so I have to set a schedule on the wall thermostat to ensure boiler runs when the TRV's calls for heat. The temperature on the wall thermostat changes 7 times a day, and when I am at home it works well. However when we leave the house and the geofencing turns off the heating, then it over shoots on return.
OK the problem is reduced in one way with a gas boiler in that is modulates, (I now have oil) but is also complicates things as well, as every time it switches off/on it takes time to adjust the modulation, so off/on switching must be reduced to minimum if your going to save fuel.
Two systems on/off and modulating can both keep the rooms in the house at the required temperature, but in the main, modulating systems do it cheaper fuel wise.
So start with boiler type and aims. But saving money is hard, if your gas bill is £300 and by all the cleaver systems you can reduce it to £250, then over 10 years you can gain if the bill for upgrade is under £400, I am allowing for interest paid on money, more than 10 years and interest also increases, so really have to base on 10 years, at £54 each for TRV heads plus the wall thermostat, it is hard to justify the expense.
I would turn off the heating when I left home, and back on at return, but then the boiler was running flat out without gaining the latent heat, but leave it on, and boiler would modulate so was gaining latent heat, so there is a balance, and under a set time away from house not worth turning the heating off.
But is seems no one has worked out what this time is. So with my oil boiler that does not modulate no question, saves money if turned off when I leave house, but not so cut and dried with a modulating boiler.