A few things...

The RN in 1941 and 1942 would not even begin to think of destroying there records and libraries. They didn't even write official doctorine for it till 1947-48 and that was after the Italians recovered some information from one of their ships sunk 5 or 6 years before. It is a foreign concept. To suddenly think they would learn a concept like this on the PoW would be to me an act of Fiction. The ship sinking in 21 minutes would not decrease the amount of material salvageable. The ship just sank to quickly , hence the loss of life. The area where it was stored was not damaged. Though Phillip's was killed that would not effect the libraries status. Just transfer the responsibility of it to the next person in the chain of command. Also all those ships sinking in one evening would not change RN doctorine in one night. Yes they will learn but the shock will take weeks to clear before anyone will think clearly as did happen historically, now even more so. Also to add, HMS Formidable is not even in PoW's protection class so wouldn't even be thought of. That's like comparing a cruiser and a Battleship in a gun duel.
If the room wasn't destroyed and the cabinets were locked up as per Battle station drill. 100% of all the documents in the cabinets will be recoverable. As I said, only reports and intercepts from the last 24 hours would most likely not have been filed. They will be very well sorted and in plain english. The shear volume of the material, if the microfiche set is present, as I think it is, it was made from the HMS Hoods files going back to when she became Fleet Flagship till around January 1941, technical manuals, intercepts, reports, legal briefs, intelligence. That will take 1000's, if not 10000's of man hours to comb through and yes it will take years to digest it all. The technical manuals will be the easiest to digest in my opinion and the ones that will be seen first. There layout hasn't changed since the IJN used them in the 1920's. The intelligence will be looked at and will make the biggest impact. If the Japanese suddenly lose trust in there radios and overreact as I think they might that too will hurt there operations for example. German's I think will just try to make things more complicated, bigger larger enigma machines, more codes. Meanwhile the reports will be the hardest to guage what they will do with and though some may read it and try to implement some ideas quickly in the first 3 or 5 months it will take at least 9 months to a year for most of it to sink in and policies to be based on it. For example I see the IJN trying to implement ASV equiped ASW squadrons by September 1942 and they might get lucky but it will be late 1942 to mid 1943 after they've used the equipment for awhile before they will become effective as what coastal command found. Meanwhile the IJN's submarine force that will most likely help train a new ASW squadron will benefit the most as they will see what deficiencies they have and come up with a list of ideas to try to make them more effective. In Germany, the KM will read the reports and technical information and be very pro-active in trying to upgrade there boats. Meanwhile the RLM will read the reports and will spend several months of recriminations and finger pointing before any meaningful work might get done ( over inflated kill reports for BoB and BoF, pilots blamed, intelligence blamed...blah blah blah ). There is also the added pandoras box that some ideas or technology alluded to in the reports and technical briefs may led both Germany and Japan to waste resouces on projects that are not and will not be viable to them during the course of the war.
Things that can be quickly done.
- AI and ASV radar sets ( IJN/IJA will have to hand make each one for at least a year, Germany will be able to mass produce )
- Shipboard and installation based radar sets ( Construction same as above ).
- radar detectors, wide range ( probably many false signals at first )
- Germany , large shell fuses, copy RN's
- IJN/IJA fuses/triggers for Depth Charges
- ASW ideas - doctorine will take longer
- New codes and signal doctorine ( this is the biggest one imho )
- Allied tactical situation known as of Dec. 1941. bases in Indian ocean not known by IJN for example now will be.

Medium term
- IJN/IJA's ideas of there planes and weapons layout. More firepower, maybe change formation tactics
- Germans develop radar homing devices to fit on new glide bombs and missles.
- Japan upgrades welding ideas and concepts
- Some tactical ideas might slowly be integrated into some of the AXIS forces. Experimentation may have happened sooner.
- German's may develop VT shells in 1943.


Long Term (?)
- They'll still be studying the reports when the allies over-run them.

This will also change how the Allies work.
- No Magic or ultra means they will have to work for there supper. More Humit, recon flights etc.
- and many more.....

That's all for now.

Russ / Roller007