The practical question in a refurbishment is usually floor height and insulation rather than preference.
Comfort and running cost
Because the whole floor emits gently, underfloor heating gives even temperatures without hot spots and frees the walls of radiators. It works at low flow temperatures, which is exactly what a heat pump wants.
On a poorly insulated floor it will simply heat the ground, so insulation below the pipes is not optional — it is what makes the system economic.
Response time and control
A screeded floor stores heat and responds slowly, which suits continuous background heating rather than short bursts. Radiators heat a room quickly and cool quickly, which suits intermittent use.
Mixing the two — underfloor downstairs, radiators upstairs — is common and works well provided the zoning and controls are set up for the two different response times.
Retrofit realities
In a new extension, underfloor heating is straightforward: insulation, pipes, screed. In an existing room, you need enough height for insulation and either a screed or a low-profile system, and the doors and thresholds have to work afterwards.
Floor finish matters too. Stone and tile transmit heat well; thick timber and heavy underlay reduce output and need checking against the manufacturer's limits.
Common questions
Is underfloor heating cheaper to run?
It can be, because it works at lower flow temperatures — especially with a heat pump. On an uninsulated floor it will not be.
How much floor height does it need?
It depends on the system. A traditional screed build-up needs considerably more than a low-profile retrofit panel, which is why it is easier in new build-ups.
Can I put it under wood flooring?
Usually yes with engineered board and the right underlay, within the maximum surface temperature the manufacturer allows. Solid timber is more restrictive.
Can I mix underfloor and radiators?
Yes, and it is a common arrangement. The two circuits need separate control because they respond at different speeds.