Thank you everyone for your repsonses, I am most grateful for your taking time to respond.
It's almost a relief to know that I am not alone in finding water vapour in the bathroom, and the outdoors an issue.
I am not sure whether that this is something that the medical profession are aware of, or even accept.
Due to intermittent claudication, lumbar stenosis and ulcerated legs, I had my bathroom turned into a wet room. The council tiok over the replacement and spent over £11k on bodging the job, and leaving me with an unusable room, with a useless air vent that serves only to bring the room's temperature down to the same temperature as outdoors.
Has anyone had any issues like this? I think mine was due to an OT report that was out of date and didn't even look at the difficulties presented by COPD.