Thanks Nun. For the sake of future users , here is the rest of the short , important thread:
Here i am with the same issue, just ordered the filter etc, cracked open the tank and there before me sat something not covered anywhere on the net, and looking nothing like any write-up I've seen, well up to the point where it states to twist open the housing and instead there are clips and looks to be a metal canister inside.
Very glad i saw your post as it saved me trying to undo the numerous clips to find that metal canister, big thumbs up for that ;o) saved me so much hassle and swearing.
Did you find out the solution, as i would be grateful to know the answer to this puzzle