"As I'm sure you realise the pound PLUMETTED from 1.31 before Brexit to a distinctly lower amount afterwards."
I am afraid the significance of 1.31 totally escapes me, That was the exchange rate in January 2016 and part of a decline from 1.42 in July 2015.That was a rise from a historic low of 1.02 in 2008. The pound presently trades at a level seen in 2010 but with reduced volatility.The point you are trying to make has no validity. Economic factors dictate exchange rates, not headlines.