Hi Jane,
I am unsure, this would depend on your bank's policy. However, given your financial situation, if there is ordinarily a bank charge, you could appeal to the bank to waive this charge, as all you are doing is seeking to repay the mortgage under the original terms and the bank is primarily concerned with having the loans repaid. When you do speak with the bank, ask for a reference number for the enquiry and the employee number/name of the person with whom you're speaking and mention that you and your husband are in financial hardship and are disability pensioners.
If the bank is unwilling to waive the charges, I suggest giving the
Financial Ombudsman Services a call and seeking their help to assist you in waiving the fees. They will act as an independent negotiator (dispute resolution assistant) with the bank to come to a reasonable resolution. This will be a free service, however, it does require you to speak with your bank first.