Re: Econ 101
The trouble is for most goods, "Buying British" is far from simple - and sadly it's that sort of bullish over simplification that's landed us in this mess.
We lack the natural resources of many of our competitors and as a country we've exported our manufacturing loading more and more or our metaphorical eggs in to the services - specifically financial services basket.
Tactically every one of those decisions was arguably defensible as a good decision at the micro level but strategically almost none ever were.
Bit of a parallel with Brexit really - The UK faces a tough choice, but as per the national idiom chooses the easy, lazy *short term* option...