Installing Direct Debit UK and Smart Debit extensions for civi 4.6
we are the extension maintainers so hopefully can help with any questions. Yes, they're actively used and installed however they're not explicitly designed to work with webform.

We've just released a 4.6 ready version of the extensions that needed it, the rest are 4.6 compatible already and should indicate so.

Let us know if you need anything else.