I have recently installed a new extractor fan in a barber's shop W.C. I used a 5inch inline type because the room is largish and the need to remove smells is great. I was pleasantly surprised by the efficiency of operation compared to a puny 4 inch sized fan. One size step up is a good move. Having a 5 inch inline fan in stock I used that. It was not a timer model, but with the use of a separate timer circuit board installed in a double pattress it works well, and is in a convenient position if adjustment is required.

www.ebay.co.uk/.../153772217901

Z.