please help! need to order quick!

[vw754]

Sorry ......need some super quick advice.......im getting this :Google "ebay.co.uk/itm/EXTRACTOR-FAN-SHUTTER-TIMER-HUMIDITY-SENSOR-150mm-M-/390012449692?pt=UK_Home_Garden_Hearing_Cooling_Air&hash=item5ace8db39c"

is it any good? Also good extraction? good make?

I know the timer will keep the fan over running(until the desired time set by me)once when the bathroom light is switched off ........how does the humidity work? is it wired different.........do humidity fans just start to work even if the light switch isn't triggered?
Any info appreciated.........as im about to press the 'buy now'............thankyou.

bathroom zone 3.............bathroom size 1.8m x1.8mx1.8m (6ft x6ft and ceiling height 6ft)