The ex-Director is in the wrong. He may still be legally entitled to the money though - 'as far as I'm concerned' is not the criteria by which that is judged.
The bank not necessarily. The bank is entitled to require a fresh mandate to be completed and to have time to process it. It's not clear even now whether that has been done.
The previous mandate will have set out the requirements for changing it - what signatures are needed to change the mandate in particular