That's not really true. The UK has run an open economy for almost 200 years and has long had one of the most diverse sets of trading arrangements of any country

That's not really true. The UK has run an open economy for almost 200 years and has long had one of the most diverse sets of trading arrangements of any country in the world. For domestic energy, it has never relied on Russia. Natural gas supplies are a roughly equal mix of domestic production, Norwegian pipeline imports, and LNG imports (primarily from the USA, but with no restriction on switching to other providers if needed). Yes, there was a spike in global LNG prices due to the Russian invasion of Ukraine but that was driven by other countries seeking to replace Russian imports. The same goes for the other areas you mentioned - food, transport, communications, and manufacturing. All have vast diversity of supply, with robust supply chains. None of them are remotely close to being dependent on a single external source.