Wind turbines - because we were slow to adopt them, other countries took the lead.
Nuclear power stations - because we stopped building them, so our manufacturers had no market. We our now buying nuclear power stations that other countries developed for their home markets.
Subs - a very small and niche market, where the politics is probably just as important as the cost.
It takes a considerable amount of R&D to develop a product, which you then need to sell a certain volume to recoup the costs. America, India, China etc have huge domestic markets that they use as the foundation for developing products. Back when we had an empire, we had a huge captive market that we used to develop and finance our products, but now we have a very small domestic market. Of course, the whole EU was effectively our domestic market, until Brexit.