An air source pump works the same way a fridge works when cooling food. The pump absorbs heat from the outside air then converts it into compressed hot air. The pump can then heat the radiator, pool, or underfloor with this hot air using this compressed hot air. Since air source heat pumps are so effective, they are preferred for underfloor heating than radiators that use a lot of energy. They can work well under low temperatures, which adds to the efficiency of these pumps. You do not have to worry about your home not getting properly heated just because the temperatures are low.

An air-source heat pump is a heat  pump that works by converting the heat from outside air into hot air to heat a room. The air from outside often has some form of heat with it, and when this is converted into energy.  It can be used to heat rooms or heat water. Air source heat pumps were invented to help cut down on the energy used by heating pumps because it uses heat from the outside air to generate heat for the pool or the home.  As long as there is enough air circulation around the pump, enough hot air will be pumped out of the heat pump. 

Yes. You can use heat pumps with radiators. If you have a big home, combining the two heating systems is more effective than using radiators or even the heat pumps. However, you will need to use more oversized radiators than regular ones if you want to reap more benefits.

You could still use them with standard radiators, but you will have to ensure that you reduce your home's heat loss to a minimum level. You could talk to a certified professional that'll inspect your home and advise you accordingly. However, you may also have to consider the radiators' energy consumption.