I initiated several redresses a number of years ago. I also ended up drafting redresses for others as a result. The basic law is contained in the Air Force Act 1955, QRs and an AP whose number I don't recall. The time limit is 3 months from the date of complaint and there are time limits for every stage. This is as a direct result of the chaos and confusion I caused by making a late complaint and taking it all the way to the top (I was allowed to petition HMTQ, but I'm not sure if that right still exists).
The staff officers ranged against me were not happy because I redressed the decision of an AVM, althought to be fair that's because I caused my original complaint to be staffed up to that level. In the end it took me 4.5 years and must have cost the MoD a fortune in time, civil service manpower etc. The RAF didn't give me what I asked for, but they did change certain aspects of their original decisions and accepted that a lot of things said in my ACRs and the staff work were just not true - I won't name names here, but I discovered the names of several liars in the command chain. Rather depressingly it took a question from my MP to get hold of my ACRs; nowadays you can't be stitched up by the disingenuous and downright dishonest persons in the command chain, up to and including a Stn Cdr as it turned out in my case, because things are supposedly more open.
My advice, with a massive amount of hindsight, is try to obtain some sort of satisfaction through the normal avenues in the command chain if that is at all possible. Redress should be last resort. The date of the final decision not to help you is notionally the date that the 3 months should run from (its based on the civil judicial review timescales).
As already stated you will find out who your friends are; don't be surprised if you lose the odd party invite. The people who turned on me the most were people who had drank an awfully large amount of my booze and eaten a lot of food at my house. I really would like to name names, but I'm saving it for a special occasion.
The other thing I learnt was to make a lot more effort with my writing. I'd always thought I was a good writer, but when you are writing for a number of civil servants and officers to read you need to be concise or they will just ignore what you have to say. Unless you have a lot of technical detail or a lot of facts confine the main body of your redress to a couple of well structured pages. Put all the niff naff detail into an annex if need be.
Hope this helps.