Thanks very much for everybody's advice.

I will definitely go for a fan sited above the shower, in the loft
and inline in the ducting. This I hope will be the quietest option.

BUT I'm still not sure what the minimum extraction rate in metres
cubed
per hour for my bathroom should be though.
I'm tempted to go for the 93 metre cubed / hour fan Richard mentioned
from cpc.co.uk (good site) but am concerned it wont be powerfull
enough.

I read up that a bathroom fan should replace the rooms air 15 to 20
times
per hour. Therefore with a room volume of 21m3 (2.7 metres high by the
way)
15 * 21 = 315m3 per hour extraction rate.
This is way higher than all the fans Ive looked at
(which are mostly 80 - 90m3)
Also bearing in mind the extraction rate drops like a stone the more
ducting you use and I plan to run it 3 metres.
Also I have a feeling that a fan with a extraction rate of
300m3 / hour might be a bit on the noisy side.

Another big pain is a lot of the pumps dont have a decibel noise level
rating so how the heck do you know how loud the thing is going to be
unless you fit the dammed thing in.

I am going to speak to a bathroom installer expert tomorrow who I have
heard sells a REALLY good fan (but for £139). I want to know why its
so expensive
and why he thinks its worth the extra money.

Hopefully I will decide after that

Thanks again
Nick