There was a time when Canada exported to the UK for charity but it was a national emergency when we did (1939-1945). The Brits paid for some of it and we forgave $4 billion of it (in 1945 $$) ... that would add up to something like a half trillion in 2019 $$ of aid of various types.They can only do that for so long before it pushes the relative value of the pound down. The market will rectify itself. After all, we don't export to the UK for charity, we do so for British pounds, and a British pound is not worth much unless we then use it for something. We could buy UK stocks or property with it, UK services, food at a Uk restaurant, or even a manufactured product from the UK. We could even sell our pound for another currency to someone else who inteds to buy it. But at the end of the day, we don't export to the UK for nothing, so if the UK imports more than it sells, then that means there are many pounds floating around waiting to be used. The owners will presumably want to use them sooner or later, no?
The Yanks made them pay up every penny with interest, btw. Canada forgave a lot of the loans. There's that "special relationship" with the USA, again.