Just going to say that the contracts for leaky ships and the design specs were actually done under labour government., Contracts were announced in 2007 but were signed in 2008 but there were years of discussion beforehand.
Building of the HMS qe started in 2009.
The financial crisis hit at the time of the build so it was decided by labour to slow the build down, which added at least 1.6 billion to the build cost.
The Tories inherited this, and it seems from what I can find the specs of the vessels stayed almost as per the original.
The Tories renegotiated the contract in 2013 due to spiralling costs, and so they felt they needed to make Bae accountable as it was assumed the government were being used as a cash cow and this contract change meant that BAE were liable for 50% of any cost over runs.
When your talking billions of £ of over runs I imagine that bae went down the cheaper route of particular items.
Those cheaper routes appear to have been with the fire system in the engine room, a faulty valve apparently, causing 3 billion of damage..