UK Politics

I've been doing a load of research on heat pumps, upcoming renovation. (Preface, Canadian living in Scotland) The issue we're having in the UK is that we've lagged behind in terms of heat pump training and installation experience. So we're in a situation where we really need to stop reliance on natural gas, heat pumps are a viable option for reducing that. Plumbing/heating firms are reluctant to recommend them, you have right wing media screaming straight misinformation or misrepresentation of facts to skew reality to fit their narrative. On top of this, a fair number of firms that do installs of heat pumps have under trained staff that are installing loops incorrectly, over complicating things, or installing HP systems in homes that are too poorly insulated. It's a self-feeding cycle of distrust in the technology.

So, from my deep dive into heat pumps. If you're dead set on classic style radiators, they'll need to be at minimum ⅓ larger, preferably larger, as you said, the temperature it's running at is significantly lower. You need a larger radiative area, and the heat pump will take significantly longer to get the room to temp. This in mind, underfloor heating is actually ideal. Radiative area the size of the whole room, with a large mass to retain the heat as it's building and continuing to radiate after the HP shuts off.
Essentials:
-proper insulation throughout, the expensive stuff, and if you end up losing some floor space because you had to false wall every room, do it.
-minimum double glazed everything.
-radiative surfaces need to be significantly larger than for with a gas boiler, underfloor heating if possible.
-look very hard into the firm you hire to do the installation, even firms with a good reputation for plumbing and gas heating may not be properly qualified to do HP installations and may make a system so complicated that any efficiency gains from the HP are lost to the point that you have no heat at all.