This excellent report contains all the information one needs to find the place - and much easier to get into now that the barbed wire and fence mesh have disappeared. One of a number of similar stores around the UK that were used to store and issue small arms ammunition - packed for immediate use. In the late 60's it was still possible to find the odd damaged ammo box scattered around - the trees and undergrowth having not yet learnt the meaning of 'rampant growth'!
Interestingly as the Cold War developed, it seems that the Authorities started to stockpile other commodities instead of ammunitions. In 1958, whilst visiting Clumber Park (in Nottinghamshire) with my parents, we stumbled on a huge storage area - small open ended Nissen huts full of wooden crates holding brown glass winchester bottles or large metal oblong tins (much like the rusty ones seen in the above photographs). Years later through my work I realised the chemicals were probably suppressant foam additives and decontaminating agents - the site being a Civil Defence Storage facility.
The large pressed-steel containers with big round holes into which a round lid would be fitted reminded me of how common they were at one time as the standard form of storage for so many things. It was one like these (but in good condition) that at one of my schools we part filled with water before dropping in a chunk of carbide before ramming on the lid. The carbide reacted with the water, and the explosion blew the lid off. Children being childish.