There's a zillion ANNEX F's out there. Possibly the OP might be referring to the old ANNEX F covering ILR applications, which had qualified disclosure several years back, but a few rogue copies snuck out into the internet.
It became obsolete when the main sections were incorporated into a Statutory Instrument in 2005. So reading it is a waste of time. Other sections not treated by Statutory Instrument are classified, and not subject to disclosure under the FOI. Even by appeal. I tried and got nowhere. The remaining sections were thrown on the skip.
But in all events, the IDI's are not statutorily provisioned, and grounding a review upon them is shakey at best; grounding an appeal on them is impossible.