Plan zzzz

Talked to Nationwide regarding what to do with "spare" funds but with interest rates between 1.2% and 1.4% we are hardly spoilt for choice. However,we are arranging to simplify our banking by dropping HSBC ( the world's local bank is now anything but local following closure of the closest  branch ) and Natwest (ditto). I have been with HSBC for over 40 years (previously Midland Bank) without complaint. The transfer process seems easy these days as the banks arrange it all amongst themselves. What could possibly go wrong ???