electric rad or under floor heating

[GREENBANK]

we have a small under dwelling type bathroom, which do you think will be the most economical electric rad or under floor heating..?? the small room is 5ft by 6ft on the large side... please and thanks

[Merriwa]

Go for a small plug in NOBO or type heater on a timer. I use 'em in isolated rooms

[buildersmate]

By UFH I assume you mean an electric system (not water-based, which would definitely not be economical to install in a single isolated room).
Both systems use peak price electricity so running costs would be similar. However unless you are able to install a decent amount of insulation under the floor coverings, you will lose more UFH downwards into the ground.
Do as Merriwa says.