Thank you very much for the above.
The fan looks excellent and seems to me to be the cheapest and best way of solving that problem.
With regard to the timer is it going to be ok to use that in the bathroom?
I purchased a ground floor flat in August 2008 which was built in 2004. I have a domestic electrical installation certificate.
In each of the two bathrooms there is an electric towel radiator with a 150w element on, I believe, a switched spur underneath each radiator.
There is also...