racedo what you say about pit wheels would be true if there were 400 units to hold stock. In terms of ac spares you miss the point that if a supplier has been allowed to let stock holdings dwindle to 0 based on historic uses and those items take 2-3 years to manufacture that is an expensive error. More embarrassing perhaps, given the general longevity of UK ac is that sometimes the skill sets required to manufacture some items have ~ literally ~ died off.
Thats where the good old contract and service level agreements come in.
Supplier responsible for holding stock ........end of story.
Any supplier who fails to do this and is audited, the Ultimate parent company and all subsidaries disbar themselves from all future contracts.