I was initially confused about reviews/appeals too. Basically this is my understanding...first stage: send in the request for a review letter stating your child's case, this must be at the Civic Centre by this Fri (I hand delivered mine, not trusting the post lately!). Should receive a reply on the 1st Dec. If it's a yes, all fine and good, but if its a no, still not deemed selective then we have the option of going through a second stage - an appeal (March time). I believe the appeal involves parent meeting with an independent panel (possibly accompanied by primary head?) and stating the case for the child again. Both panels see child's work as far as I can tell. According to Chatham Grammar, to whom I spoke yesterday, the grammar school in question may also contribute to the discussion (not sure whether that is in person or not). Not sure when the appeal decision is made, forgot to ask that! Also, you can appeal to/for than one grammar as far as I know.
Hope that helps in some way, and good luck.