On Tue, 27 Mar 2018 13:32:38 +0100, Pete Zahut wrote:

Apart from a central heating radiator, which we can't do (and even if
we could, the central heating won't be on during the night so it's a
non-starter anyway), what's the best type of heater for in a bathroom?

Central heating not on during the night?

How about leaving it switched on all year round and using programmable
thermostats and zoning?

Can't afford it? Then improve the insulation levels.

If the other residents don't mind then leave the door open and heat the landing
or hallway.

Best heater for a bathroom? One that keeps the room warm for when its going to
be used. With lots of decent insulation, maybe some solar gain, a closed door
and a small source of heat like a towel rail you could possibly keep the room at
reasonable comfort levels round the clock.
--