Radiator check
A common worry about heat pumps is having to replace every radiator. Often the ones you have are big enough. This tool says which rooms are likely fine, which might need a deeper radiator in the same space, and which might need a bigger one.
What you need
About five minutes, starting at your boiler and then going round the house. You'll find the heating temperature on the boiler, and look at how far each radiator sticks out from the wall and how thick its pipes are. There is nothing to measure and no postcode.
What it can't tell you
It works from how your radiators cope with the boiler today. It doesn't know how much heat each room loses, and it assumes each radiator is only just big enough for its room, so its answer leans cautious.
If the answer rests on guesses, the tool suggests turning the boiler down for a week of cold weather. That tells you more than any calculation: if every room still gets warm, the radiators have capacity to spare. An installer's room-by-room heat loss survey gives the real answer, and a heat pump is designed from it.
What next
The heat pumps page explains why a heat pump runs radiators cooler. A room that needs a bigger radiator may not after insulating it. Choosing an installer says what a survey should include.