Evenin' all,
It's not often I rave so much about a product however, I think this one is worth mentioning.
Recently we had our bathroom redone, it had a 4inch extractor fan fitted through the wall, this could only be described as utter s**te. It was noisy and had very little effect.
So I purchased a Vent Axia ACM100T and finally got round to fitting it, when I turned the electrics back on to test it I thought it wasn't working; it was that quiet! It does a fantastic job of clearing the steam and there is no condensation on the tiles at all after showering. I have it connected to a roof/vent tile for the exhaust and a disc air valve for the inlet, all with flexible insulated ductwork and it copes very well with this. I could have done it with smooth plastic ductwork but it really wouldn't be easy to do in the tight space I had.
If you're looking for an in-line fan, I would definitely recommend this :)