Just over one million Cheshire, Derbyshire and Dunfermline customers are to be moved to Nationwide, after the building society announced plans to scrap the three brands.
New Nationwide banking customers who've been abroad in the past month should check their statements now to make sure they haven't been charged a non-sterling fee for purchases made in the UK.
Santander has earned the unwanted crown of being the most complained-about banking firm per customer, figures from the Financial Conduct Authority (FCA) show.