Put that economics handbook in todays perspective, will ya? We live in a globalized world where majority of things we buy is produced in one country (China). Because how capitalism works and because of complexity of processes used in pretty much every industry today, it is not possible to start producing goods in our native countries. We don't have the tech, we don't have enough personnel, we don't have resources and even if we do, we aren't keen on extracting them on our soil. Lastly, we want to be paid well for our job and them Chinese still do it for less money. Actually people in Serbia can compete with them when it comes to salaries, but we don't have anything else to offer.
Due to strained relationship between government of your country and China you're actively seeking someone to replace them. Your best bet is India, but they are too far from being able to compete with Chinese on many fronts. Maybe in few decades, but short and medium term we all are stuck with Chinese being our only manufacturer.
What do you suggest British to produce, now they are free? Which goods? You're advocating same communists did for decades, rely on our own food, our own industry, buy home made products say no to imported goods. Well, it just doesn't work that well.