In fact, so many we can't see the trees for the forest.
How do control and limit Xmas Trees? Implement DGDQA Standing Instruction - 0136. MoD don't like this, as it's the one that gives lie to the fallacy that only Commercial can commit MoD to a contract. But it's the project manager's primary tool to control the standard and cost of repairs. Ignore it at your peril. That they do, places people in peril.