What power and type of in-line bathroom extractor fans should I be looking for?
In the end I went for a mixed flow (which I think is both cetrifugal &amp; radial or something), has about double the throughput that is recommended for the size of room (240 m^3/hr vs 110 m^3/hr). Doesn't have a timer on it, but it seems to be keeping the steam down when we shower anyway.

Here's a link to the fan I bought in the end.

Thanks for the pointers.