Exactly. Heats the place up FAR quicker than a heatpumps too. Heatpumps only heat the water to something like 55c which is the reason you need giant radiators for them. It actually isn't hot enough to kill leagionella bacteria either, but like the government, let's just gloss over that for now.
Even at places like screwfix the heat pumps are now 65c models.
Realistically you don't want rads more than that as a max anyway.
Efficiency is gained by being lower.
You don't need giant radiators at all, you need suitable radiators based on your house and the effectiveness that it retains heat.
heat pumps can go to over 100C, ie superheated, although the only ones I have seen were in effect two part systems (2x compressors)
the heat pump is courtesy of tax payer subsidy too, if that wasn't in Kiers 28BN, subsidies which are also contributing for the chosen ev companies to
provide domestic battery production and avoid the future impact of rules of origin, itself an impediment for achieving 22%, as the other companies may remonstrate.
Basically irrelevant if your replacing your boiler with a heatpump, its what you pay that matters not the true cost.
Things like solar have showed that they need subsidy, until they don't.
Nothing wrong with a nicely sized modulating combi.. ours freed up loads of room in the loft and airing cupboard, it's been nearly 20% cheaper to run for us...
If I go 'heat pump', I'll go air to air so I can cool as well and run that off battery storage charged overnight on a cheap EV tarriff..
You wouldn't have saved 20% if you had bought a modern system boiler with tank as they have the same efficiency, literally the boilers are all listed as the same efficiency.
There is a marginal loss of energy from the tank (its truly very low now) but you missed the massive quality of life benefit of a system over a combi.
When my boiler did break down the other year (was actually a diverter valve) the fact I could still have a hot shower for the 48 hours it took to get fixed was a god send

I relished every second in that hot shower.