My overdraft is there simply to catch my direct debits if I have to sail too close to zero one month.
(If you’re using your overdraft just to buy stuff, you’re getting life wrong.)
Your mortgage payment is pretty much the monthly bill you never, ever want to miss. One hint that you’ve had any kind of problem meeting that and you’ll find getting another mortgage or remortgage more expensive or impossible.
I’d rather sort my budget out the next month than have to tell the bank I can’t pay my mortgage, and you can’t do that on a credit card.