Your not the only one buddy.
I dont suppose you purchsed your kitchen from Rock Solid Kitchens, as this is by far the worse customer service company I have ever experienced in my life.
I have the same extractor fan and like you are also missing part of the 90cm chimney, I have searched all over for spares but to no avail, therefore after failing to receive ANY response from the kitchen supplier 'Rock Solid', who I am contracted with, I am issuing a county court summons for the recovery value of the extractor fan amoungst other faulty/missing items as under the Sales of Goods Act they have not complied.
If they fail to answer to the summons, the baliff will go in and recover business assets, so worth while for the sake of £69 court cost.
Eddie, November 2008