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.

[1] https://www.amazon.com/Seapower-States-Maritime-Continental-...