After years of being at the bottom end of the Westland spares chain and laterly 8 years of service from ECD and MD lead me to the conclusion that you get what you pay for. If you've got a huge pile of cash doing nothing, you buy a box of spares and 'never' have to wait for extended periods.
The MOD method seemed to be to equip a Squadron with 12 heli's and only fund 66% of them for peacetime use, just strip bits off the 'hangar Queens' in the short term whilst you wait months for actual spares to arrive! Of course when you then deploy to sandy lands you start with a fleet of run down hangar queens before the enemy try to reduce your resources.
The Police system (no Hangar Queens available) is to pay into a pot along with other like minded operators in advance for a promise that items will be made available in good time. This approach often works.....
regards to all.