… and should it happen … you will marked for ATC-HQ 'special attention.
In respect of my previous postings, this is the other side of my points whereby this is the responsibility of the new CivComm and you cannot expect the CO to undertake the role.
The advice to date gravitates toward phone calls and speaking to the bank. I doubt you will make progress with the bank as the laws that now bind them will be a greater concern to them (in terms of penalties etc.).
Despite the difficulties surrounding your outgoing chair you will have a fairly stark decision 1/. swallow hard and engage in the hope that your patience can win the day 2/. walk away, start new bank accounts and go from there. This is not an uncommon situation and one understandable reason why ATC-HQ feels a need to involve itself in squadron charities. However, be careful if your bank asks for a copy your constitution. If you present them with the current ACP-11 you will probably rejected as the wider provision for signatories is contrary to banking rules (I can quote three high street banks who have made this observation in our trials).
I certainly do wish you luck and patience and that common-sense will prevail. Without that, you are very unlikely to be able to recover control of the bank accounts from the current signatories if they will not respond.