I don't buy the blather put up by the Govt about them being to expensive to cancel
Whether you "buy it" or not is pretty irrelevant, fact is the contract cancellation fees would be more than the completion costs. The desire would appear to have been there to cancel them, but they wont because of the cost.
The Navy shot itself in the foot; they wanted too much and had not enough to pay for it. In an ideal world, we would have carriers and Harriers, but it isn't. We have to cut our cloth etc etc.