The pound will go down,no doubt about that.But as I understand,FXB would mean short the pound long the dollar which can make it a bit tricky.It will be a race to the bottom.This is why I didn't initiate a short and the FTSE is energy company heavy,so risky as well even though the macroeconomic picture of Great Britain is very bleak.Maybe a better combo will be long Australian dollar,short British Pound(long commodities play,short over leveraged housing market).Correct me if I am wrong.Just my two cents.