Your GBP direct debits will still be collected normally using your account number and sort code. Since at this moment, we only allow you to set up GBP DDs in the UK using your GBP local account details, and considering that we're only changing your IBAN (used in this case for GBP SWIFT transfers), those details will remain the same. As such, all the GBP direct debits that you have set up at this moment won't be affected at all by this migration.
As for your EUR direct debits, please, make sure you have updated the account details with the merchant! We understand that this can result in some extra work for you, and we apologise for any hassle this may cause in advance. This change was necessary so that we can continue to provide our services to you and our European customers after the end of the migration period of Brexit. We’ve been working hard to keep all accounts and functionalities just as you are used to. Inevitably this means that we need to ask for your efforts on this as well, meaning that by the end of the migration, you will need to update and share these details with your customers, partners, and any merchant connected with active direct debits currently in place.