I'm not British, but it is my understanding that after WW1 and WW2 the money had just dried up when it came to capital-intensive projects. I've just finished reading a book [1] that explicitly mentions the lack of available money as a reason for the Brits having to give up their Sea Power status just after WW2.
This was certainly a real problem, as was the whole IMF rescue business in the 70s, but not across the whole postwar period. More could have been done with the oil wealth than turn it into a real estate boom, for example.
Realistically the UK gave up sea power status sometime during WW2 when we were massively outbuilt by the US, and the collapse of imperialism as a ""business model"" took care of the rest by making us fall back on our own resources rather than simply taking them.
[1] https://www.amazon.com/Seapower-States-Maritime-Continental-...