Can I have unused credit returned to my bank account?

No, unfortunately, this is not allowed*. You can transfer/resell your credit to another Pay2Wash user via My Account > Transfer credit. (You will have to arrange a fee for this amongst yourselves.)

* If we would allow users to deposit and withdraw money from their account, we would be providing a service similar to that of a bank. According to the "Financial Supervision Act" (Dutch:"Wet op het financieel toezicht") this is therefore not allowed.