RuairiG:
Use the heating system. The electric heaters can be very expensive to run, so each room occupant will end up paying more, than they would have to chip into a communal utility bill fund.
With the heating system on, the heat can last longer, as it heats the building through all the pipes and radiators. Whereas with electric heaters, although you get instant heat, the heat can dissipate quickly. So you end up sat in front of the electric heating, keeping it on for longer.
If the heating system is not adequate, I would recommend the oil filled electric radiator type heaters. I think the best ones are made by Delonghi and some come with a timer and thermostat, so you can use it as a top up.
Huckster