Does iATS payment requires SEPA Direct debit for ACH to work?
We did build UK Direct Debit [with the mandate - the entire workflow] into the iATS Payments Extension but it wasn't used much and we have not actively supported it recently. And SEPA works well and is widely adopted by lots of European CiviCRM Clients. One does not need to be exclusive -> you can processing CC with iATS Payments and use SEPA for DD for the time being.