Just to update this thread.
The PSU Fan started to only work now and then, and in between times would get really really hot! And on googling I found ppl having problems with fitting different fans - and this one didn't seem to be available fps350-60mdn .
So anyway I found one on ebay very cheap and its fitting and working, lovely cool case now
And this guy seems to sell alot of them so just incase anyone else has the same problem, there is the answer