Globalisation isn't only (or even mainly) about technology, manufacturing and production. economic freedom and free trade are ends in themselves - it can, arguably, produce higher levels of overall material wealth worldwide and the spread of liberty (and capitalism). An inward looking Britain trying to become self sufficient is a massively retrograde step, out of tune with a world that's heading the opposite way. Renault's beef with brexit was about trade barriers. so, you envisage an automated manufacturing plant producing toothpaste for the same cost of a replica of it in Vietnam? I don't think so, the same quality staff, same quality professionals, but a currency that's 27000 times cheaper (and, in dollar terms labour and manufacturing that is too). what then, a Britain that imitates putin's Russia and in some misguided fit of patriotism produces all its own stuff for much more (in dollars)?
i'm an immigrant. I feel it's entirely not my business that the British economy has invested so much in financial services. perhaps it could have, as part of the eu, developed a different kind of developed economic infrastructure. but to start competing with india and china as manufacturing hubs of the world would be a mistake, to put it politely.