Avenger
I got a mortgage in Singapore Dollars from Lloyds in Singapore to buy a flat in London in Pounds for my son and daughter. My salary was in Singapore Dollars so no problem.
Surely the answer is to get the mortgage in the currency your salary is in based on the exchange rate at the time. I left Singapore whilst mortgage was running but paid it off a few years later but the exchange rate at the time was in my favour but it could have been to my detriment if I had left it a year or so later.