Advice for a very cold bathroom.

[Superspudking]

I'm looking for a bit of advice on how to warm my bathroom up a little or as to why it is so cold. It's an internal bathroom in a new build flat (5 yrs old now) it has alway been cold but I've previously been to lazy to sort it.

So like I said its am internal bathroom with the 4 walls backing onto communal hallway, fire corridor vent, bedroom walldrobe and flats hallway.
All ways and floor are really cold to touch so I'm not sure if its loosing heat through a surface or through the fan

I've have previously replaced the ceiling extractor fan to one with back draught flaps but that didn't help. The extractor fan Is located pretty much above the sink and about 1ft-2ft from being above the radiator.

Am I best to relocate the fan above the bath/shower?
Am I best to use a humidify sensor fan?
Can I fit any other back draught devices?
Can I fit any membrane under the floor?

Any advice is much appreciated

Thanks
Spud

 

[MANDATE]

You've not mentioned the radiator.
Is the output from it restricted, is the lockshield valve closed too much.
Is it a single radiator that can be replaced with a double. or even a larger single.
What about insulation, any chance of insulating the ceiling

 

[petertheplumber12]

You need a special rated fan to go above the shower, it has atube that connects to the ceiling and then the fan and then more tube taking it out. That would be a good idea anyway.