Deductions from UC for service charges

We run supported housing.  In many of our addresses, claimants are in receipt of ESA/JSA and pay their ineligible service charges via Third Party Deductions taken from their income benefits.

We have an increasing number of residents in receipt of UC income (albeit their eligible housing costs are paid via HB rather than UC as it is supported housing).

Third Party Deductions for ineligible service charges should be available to be taken from UC via a prescribed form.  We have sent a number of these requests via post over the last 6 months but to date none have been set up.
Has anyone else had any luck with this? 

We have an email process set up for TPDs from JSA/ESA claims.  Emailing speeds up processing, ensures no forms get lost in the post and also provides an email trail to chase up.  Is there a centralised email address that we can send requests to for UC TPDs?

Thanks

See this from a couple of weeks ago:

https://www.rightsnet.org.uk/forums/viewthread/11723/

I think he is right: the only way to collect hostel charges not in arrears is to approach it as a generic discretionary APA.

Thanks HB Anorak, and apologies I hadn’t seen the existing thread.
Nick