This is a temporary procedure, and will change once a better procedure is in place.
To change your bank details:
1. Call GoCardless on 020 7183 8674;
2. Their representatives will ask you for your email address you used when setting up the Direct Debit;
3. Tell them which Direct Debit you wish to change;
4. They will then ask you for your new bank account (8 digits) and sort code (6 digits).