Corelli Barnett wrote a whole series of books about the UK, before, during and after WW2. I strongly recommend them to anyone who wants to understand modern Britain and how we got here. In fact, if I was PM, they would be compulsory reading in secondary schools.
On the UK shipbuilding industry - in a nutshell, it failed because it was shite. Customers found they could get ships cheaper (and built on time, not delayed) from other countries. So they took their business elsewhere.
Whether you are in or out of the EU, if your industries are obsolete and uncompetitive, they will not be able to compete. Fancy that! However, if you have a North Korean or East German attitude you can force your home consumers to buy shite, but that's as far as it goes. Does anyone fancy driving a Trabant?