Direct Debit Fraud

A recent cash flow glitch at the local Conservative Party led me to check a couple of the less active bank accounts in search of funds. These are the accounts intended only to receive standing order receipts.
So payments from the accounts immediately look suspicious. Further enquiries revealed a whole series of fraudulent direct debit transactions. Charges for pet insurance, mobile phone insurance, magazine subscriptions, RAC breakdown cover, etc.
The accounts details are displayed online via the Party membership subscription forms.
Apparently the banks turn a blind eye to direct debits set up online (without a signature), even if the address does not match. As long as the amount is relatively small -- say under £50 -- all they process is the account number and sort code.
We’re trying to get our money back.