Tuc, I recall seeing lots of sealed packs of helo spares at Finningley around 1990. IIRC they were dated around 1963 so guess they were for the old Whirlwind.
BB, on holding stock that never moved: I recall watching an OU TV programme in the late 70s that covered the issue of stock holding. The programme left a lasting impression. The case they used was the coal mine. One item was nails. The nails were cheap but were used in huge quantities every week. The reordering and supply was quick and simple. The result was there was no need to hold more than a week or so stock.
However a pit winding wheel cost a huge sum of money, around £120k at the time, but may not be required more than once every 18-24 months. Clearly the cost of holding was significant. However the time to order and receive a new winding wheel was in the order of 3 months and set against the loss production and profit was significantly greater.
The conclusion was that it was necessary to hold long lead time and expensive items if the consquential loss was greater.