What extractor fan for small understairs wc

[fingertight]

Hello chaps

I'm hoping for some advise on what fan I need to get for the understairs wc I'm doing at the moment. The fan route itself will need to go through a cavity wall then rise up in a wide stud partition around 1 meter high, then either terminate on a pitched roof or further onto an external wall. I was wondering what fan would be up to the job, which also looks nice and small too? Any advise is appreciated

 

[ban-all-sheds]

The bigger the better.

All (or nearly all?) fan performance data quoted by the makers assumes no ducting, and a long run with bends and then some sort of outlet fitting will reduce performance considerably.

Go too small and you risk making it pointless.